The top 10 biggest Champions League shocks of the 21st century: From Jose Mourinho's Porto stunning Man Utd to Chelsea's Camp Nou miracle

UEFA Cup holders Porto qualified for the knockout stages of the Champions League after finishing second in their group behind Real Madrid, and were rewarded with a huge tie against Sir Alex Ferguson's Manchester United.

The Red Devils were expected to blow past the Portuguese side, but Jose Mourinho's team flipped the script at Estadio Do Dragao. Porto won the first leg of the last-16 encounter 2-1 thanks to a Benny McCarthy brace, with United's misery compounded by a red card for Roy Keane.

United had to make do without their captain for the return leg at Old Trafford, but they still managed to put one foot in the quarter-finals thanks to a first-half header from Paul Scholes. The hosts held onto their lead until Porto won a free-kick 25-yards from goal in stoppage-time.

McCarthy tried to bend the ball into the top corner, but didn't quite get enough pace on it, and Tim Howard really should have made a simple catch. Unfortunately for United fans, the American fumbled, and midfielder Costinha was on hand to turn the rebound into the net.

Mourinho leapt from his seat in the dugout and ran down the touchline to celebrate with his players as Ferguson was left speechless. Porto captain Jorge Costa aptly summed up the incredible scenes in his post-match interview: "When Costinha scored, I was going crazy. Mourinho was going crazy. Everybody was going crazy."

Porto would go on to win the tournament, beating fellow underdogs Monaco 3-0 in the final. Mourinho then made the jump to Chelsea, renewing his rivalry with United and Ferguson in the process.

Real Madrid looked nailed on for a place in the last eight of the 2018-19 Champions League after beating Ajax 2-1 in the first leg of their last-16 tie in Amsterdam. Confidence should have been high in the Real ranks after Marco Asensio's late winner, but they allowed complacency to creep in at Santiago Bernabeu.

Ajax stunned Los Blancos by racing into a 2-0 lead inside 18 minutes, with Hakim Ziyech and David Neres scoring the goals. Dusan Tadic made it three just after the hour mark with a brilliant curled strike from just outside the area, leaving Real with a mountain to climb.

Asensio pulled one back in the 70th minute, but Lasse Schone scored a spectacular free-kick to put the game to bed for Ajax moments later. Nacho was then sent off for a second bookable offence as frustrations boiled over for Madrid late on, with the Dutch giants ultimately holding on for a famous victory.

Real were sliced open in the absence of Sergio Ramos, who was handed a two-match ban for deliberating forcing a yellow card in the first leg. But even if he had been available, it seems unlikely that the Spanish giants would have stopped Ajax.

Erik ten Hag's exciting young team repeated the trick against Juventus in the quarter-finals, winning 2-1 in Turin before picking up a 1-1 draw at home to progress. Ajax were the victims of an incredible Tottenham comeback in the semi-finals, but their unlikely run was still the biggest story of the European season.

After signing from Fiorentina in January 2022, Dusan Vlahovic scored the quickest-ever goal from a Champions League debutant to give Juventus the lead after 33 seconds against Villarreal at El Madrigal. Dani Parejo scored a second-half equaliser for the Yellow Submarine to level the last-16 tie, but there was a general feeling at full-time that Juve had already done the hard work in Spain to qualify.

Massimiliano Allegri's side pushed for a winning goal right from the off in the second leg at the Allianz Stadium, while Villarreal seemed happy to sit back and absorb pressure. They defended deep and in numbers throughout the second half too, but sprung into life just as Juve started to tire.

Substitute Gerard Moreno broke the deadlock from the penalty spot in the 78th minute, and Pau Torres stunned Juve with a close-range finish to double Villarreal's lead four minutes later. Arnaut Danjuma then had the final say in stoppage-time as he also converted a penalty after Matthijs De Ligt was punished for a handball in the box.

Allegri struck a bitter tone after the game, telling reporters: "Villarreal defended with 11 men, clearly trying to bring the game to extra-time. Then that goal changed everything."

Deportivo's 2003-04 Champions League campaign was quite the rollercoaster ride. The Spanish side finished second in their group behind Monaco, who battered them 8-3 at the Stade Louis II in one of the craziest games the competition has ever seen.

They shored up their defence in the last 16, however, to beat Juventus 2-0 on aggregate, which set up a blockbuster quarter-final tie against holders AC Milan. Deportivo then made a dream start in the first leg at San Siro.

Walter Pandiani fired Javier Irueta's side ahead after just 11 minutes to silence the home crowd, but it would prove to be a false dawn. Milan's class shone through in the end as a Kaka double and goals from Andriy Shevchenko and Andrea Pirlo wrapped up a comprehensive 4-1 victory.

The Rossoneri should have been home and dry, but this Deportivo team didn't know when to quit. Pandiani scored another early goal in the return leg at Estadio Riazor, and this time they didn't buckle.

Juan Carlos Valeron and Albert Luque made it 3-0 before the break, and club captain Fran added a fourth in the latter stages of the game to cap a remarkable performance. Irueta said after the final whistle: "The game turned out exactly the way I dreamed. It was almost mission impossible."

Eventual champions Porto knocked Deportivo out in the semis, but they were already winners in the eyes of their supporters. The memory of Milan's capitulation has never left former boss Carlo Ancelotti, who said in 2017: "I want to forget, but I'm not able to."

No one expected much from Sherrif Tiraspol when they made their Champions League bow in 2020-21. The Moldovan side, though, won their first group game 2-0 against Shakhtar Donetsk, albeir the real test was still to come.

Sheriff arrived in the Spanish capital to face Real Madrid on matchday two, and the gulf in class between the two teams was evident from the first whistle. Carlo Ancelotti's side dominated possession and peppered the visitors' goal with shots, but they held firm and looked for opportunities to counter.

Jasurbek Yakhshiboev stunned Real in the 25th minute, heading a cross past Thibaut Courtois at the back post to finish a quick breakaway. Karim Benzema eventually equalised from the penalty spot mid-way through the second half, and the hosts continued to press for more goals thereafter.

But they were caught by a sucker punch in the game's final minute. Sebastien Thill found the top corner with a thunderous half-volley from the edge of the box, sparking wild scenes of celebration in the away dugout. It was a goal worthy of winning any game, and one that left Ancelotti bemoaning a lack of fortune for Real. "Everything went well for them; everything went wrong for us," he said post-match.

Unfortunately for Sheriff, they peaked too early. After subsequent losses to Inter, Madrid gained their revenge with a 3-0 win in Moldova. Sheriff crashed out after a 1-1 draw away from home against Shakhtar on the final matchday, while Los Blancos qualified as group winners and went on to win their 14th European Cup. But Sheriff fans will always have that special night at the Bernabeu.

Prior to their appearance in the 2020-21 Champions League final, City had been hugely disappointing on Europe's biggest stage. They were dumped out in the last 16 by Monaco in Guardiola's first season in charge, and then lost against Liverpool and Tottenham, respectively, at the quarter-final stage in 2017-18 and 2018-19.

City looked poised to change that dynamic the following season, as they stormed through the group stage unbeaten before claiming the scalp of Real Madrid in the last 16. The Covid-19 enforced break in the campaign also appeared to work in their favour.

Two-legged ties were scrapped for one-off games at neutral venues for the quarter and semi-finals, with City handed a favourable draw against an unfancied Lyon side in the last eight. But Guardiola would end up being the architect of his own team's downfall.

In an apparent attempt to catch Lyon off-guard, he opted to play three at the back and named key creators Bernardo Silva, David Silva, Riyad Mahrez and Phil Foden on the bench. City looked lifeless in the first 20 minutes of the contest as a result, and it was no surprise when Maxwel Cornet opened the scoring for Lyon with a smart finish from 20 yards.

Kevin De Bruyne levelled proceedings when he swept a first-time shot into the far corner after being set up by Raheem Sterling in the 69th minute, but substitute Moussa Dembele restored Lyon's lead 10 minutes later, despite complaints from City that VAR had missed an obvious foul in the build-up.

City surged forward in search of another equaliser, but when Gabriel Jesus squared for Sterling five yards out and he somehow skied the ball over with the ball at his mercy, there was a sense this wouldn't be their night. And so it proved, as Dembele tapped in his second three minutes from time after Ederson failed to hold a tame Houssem Aouar shot.

"We will keep trying, and one day I am sure we will be able to bridge this gap," Guardiola said after the defeat. De Bruyne's reaction more aptly summed up the general mood of the squad, though, as he added: "Different year, same stuff."

The 2009-10 season was a strange one in many ways for Barca. They picked up a total of four trophies, including La Liga and the Club World Cup, but were ultimately judged on their failings in the Champions League.

Mourinho's Inter knocked the reigning champions out in the semi-finals, and the loss was made all the more painful due to the Zlatan Ibrahimovic-Samuel Eto'o swap deal the previous summer. Ibrahimovic never settled at Camp Nou and had a fractious relationship with Guardiola, which ultimately disrupted the harmony in the dressing room, while Eto'o was one of Inter's best players in their treble campaign.

Barca's defence of the Champions League started well enough, as they drew 0-0 with Inter at San Siro in their group-stage opener before beating Dynamo Kyiv 2-0. But Rubin Kazan touched down at Camp Nou on matchday three looking to make a name for themselves.

It only took them 120 seconds to prove their mettle, as Aleksandr Ryazantsev fired Rubin ahead with an outrageous long-range shot that flew into the top corner past Victor Valdes. Ibrahimovic drew Barca level early in the second period, but Rubin would not be denied.

Gokdeniz Karadeniz scored another brilliant goal on the counter for the Russian side in the final 20 minutes, and they held on for all three points despite a late assault from Barca. Rubin's celebrations were somewhat muted after the final whistle given the magnitude of the result, but their head coach Sergei Ryzhikov offered an explanation.

"We gave so much that after beating the best team in the world we had no strength to celebrate," he said. Guardiola, meanwhile, was left lamenting his side's lack of cutting edge, as he told reporters: "With the statistics that we had, in any other sport we would have won, but not in football."

Barcelona haven't won the Champions League since 2015, and have fallen to more than a few surprise defeats since then as financial problems have threatened to swallow the club whole. The worst of them came in 2018, when they faced Roma in the last eight.

The Giallorossi had punched above their weight to make it to that stage, and it showed in the first leg at Camp Nou. Barca ran out 4-1 winners, with Luis Suarez among the scorers as they put on a feast of attacking football.

But Edin Dzeko's away goal would end up proving crucial. Roma were a completely different animal at Stadio Olimpico, with Dzeko prodding them into the lead in the sixth minute after latching onto a high ball that completely bypassed the Barca defence.

Daniele De Rossi scored a penalty just before the hour mark to really give Roma hope, and they continued to force the issue as Barca struggled to put together any meaningful patterns of play. The home side got the third goal they deserved eight minutes from time, as Kostas Manolas beat Nelson Semedo to a corner at the near post and glanced a superb header into the far corner of Valdes' net.

There were tears in the stands when the referee blew for full-time, and there was also an outpouring of emotion on the pitch as the coaching staff joined in to celebrate with the players. Ernesto Valverde was humble in defeat, as he said when asked why his Barca side crumbled: "They played well and we didn’t. They stopped us playing our own way."

Manchester United suffered their second Champions League final defeat to Barcelona in the space of three years in the 2011 showpiece, which ultimately marked the end of an era. The Red Devils haven't been beyond the quarter-finals since, with their lowest point in the competition coming during Sir Aelx Ferguson's penultimate season at the helm.

United were handed a relatively straightforward group on paper, alongside Benfica, Basel and Romanian minnows Otelul Galati - who were making their first-ever appearance in the competition. Ferguson's men comfortably beat Otelul home and away, but drew both their matches against Benfica and were also held to a draw by Basel at Old Trafford. That sequence of results left them needing to win in Switzerland in order to be sure of reaching the last 16.

United made the worst possible start as they fell behind to a ninth-minute strike from Marco Streller, which came after some questionable defending and a poor attempt to clear the ball from David de Gea. The visitors then lost talismanic captain Nemanja Vidic to a serious knee injury, and the writing was on the wall.

A young Xherdan Shaqiri was a menace for Basel throughout the match, and he provided the cross for Alexander Frei to nod in their second goal in the 84th minute. Phil Jones halved the deficit in the final minute, but it was too little too late for United, who dropped into the Europa League, much to Ferguson's frustration.

“It's a competition I've never been in with United, it means a lot of Sunday games and that's not ideal. That's our penalty for not qualifying tonight," he said. Basel went on to beat Bayern 1-0 at home in the first leg of their last-16 tie, but suffered a humbling 7-0 loss in the return that further illustrated how poorly United had performed in their group.

The 2011-12 season was one of major highs and lows for Chelsea. Andre Villas-Boas was sacked after just eight months in the managerial hot seat as the Blues slipped out of contention for a top-four finish, with his assistant Roberto Di Matteo handed the reins until the end of the campaign.

Di Matteo was a popular appointment, having enjoyed a stellar spell at the club as a player between 1996 and 2002, but no one could have predicted how big an impact he would have in such a short period of time as caretaker boss.

Chelsea came back from 3-1 down to beat Napoli 5-3 on aggregate in the Champions League last-16, and then got past Benfica with minimal fuss in the quarter-finals. Defending champions Barcelona were up next, and they were considered as heavy favourites to go on and retain their European crown.

The Blaugrana had 72 percent of the ball in the first leg at Stamford Bridge, but Chelsea won 1-0 thanks to a Didier Drogba goal, which came from their only attempt on target in the game. Many pundits still fancied Barca to get the job done at home, and everything went according to plan for the Catalan club in the first 45 minutes.

Sergio Busquets and Andres Iniesta found the net for Barca either side of a needless outburst from John Terry that saw him shown a red card for violent conduct, but Ramires grabbed a vital away goal for the Blues in first-half stoppage time. It was a wonderful effort too, as the Brazilian chipped Victor Valdes after playing a brilliant one-two with Frank Lampard.

Barca made their numerical advantage count in the second period as they pinned Chelsea back in their own half, but luck appeared to be against them. Lionel Messi smashed a penalty against the bar and hit the post with a later effort as the Blues held on, before Fernando Torres popped up in stoppage-time to make sure of their progress.

A long clearance found Torres on his own in acres of space just inside Barca's half, and he showed great composure to stride through on goal and round Valdes before tapping into an empty net. Gary Neville's famous commentary for Sky Sports added even greater weight to the moment, as the United legend had what became known as a 'Goalgasm' when trying to get his words out.

Di Matteo hailed the team spirit in his squad after the wild celebrations that followed the final whistle. "The belief was always there - we wouldn’t be in the final if we didn’t believe we could get there," he said.

That belief carried Chelsea all the way to their first-ever Champions League title, as they beat Bayern Munich on penalties in the final at Allianz Arena. Di Matteo also delivered the FA Cup to complete a remarkable double, and although he was dismissed after a poor start to the following season, his status as a Blues legend will always be secure.