Trent Alexander-Arnold MUST lock down electric Luis Diaz in Real Madrid's blockbuster Bayern Munich tie - or he can kiss his England World Cup hopes goodbye

Diaz's arrival on Merseyside in January 2022 brought an extra spark to Liverpool. It was clear that Sadio Mane was likely leave the club at the end of that season, and while Spurs were ready to strike for Diaz after some impressive displays for Porto, Liverpool got in early to ensure their Mane succession plan was secured before the Senegalese even left Anfield.

"It is always exciting when we get a new player in to see how he will fit in, how he plays, how he is in training, what he is about, but he's fit in straight away," Alexander-Arnold said of Diaz two weeks after the Reds shelled out just shy of €50 million for the winger.

Diaz's adaptation to the Premier League, admittedly, took a bit of time, but his connection with Alexander-Arnold was immediate. The right-back assisted him on just three occasions during the three seasons they shared on Merseyside, yet the creative understanding was clear from early on. A common sight as Jurgen Klopp's Liverpool tactically evolved would be Alexander-Arnold drifting inside and playing a raking pass to the left flank, which Diaz would eagerly ran on to.

And, of course, the two shared immense success on the pitch. During three-and-a-half seasons together, they won two League Cups, an FA Cup and the Premier League.

A few eyebrows were raised when Bayern, historically reluctant big spenders outside of the Bundesliga, shelled out €70m for Diaz in July. With Jamal Musiala having picked up a gruesome injury at the Club World Cup, there was a space in the Bayern attack that needed filling short-term, but it still felt like a major investment on a player who would turn 29 in January.

Vincent Kompany had a vision, however, and things have run swimmingly thus far. Harry Kane, while remaining Europe's most potent goal-scorer, still has the freedom to roam and drop deep, to pick out passes. When he does, Diaz uses his blistering pace to make runs in behind. But when teams go into a low block, Diaz still has the necessary trickery to find space, pick a cross, and set up his team-mates. It's something Kane highlighted as early as August.

"Lucho, you know, it's only been a few weeks but I feel we have an instant connection," Kane said after Diaz assisted him twice against RB Leipzig. "He's got a couple of assists there for me today [and] he finished his goal off really well."

And Diaz hasn't really slowed down since. He now has returned 40 goal contributions in all competitions, averaging 1.08 goal contributions per 90 minutes. Both are career-best marks, and nearly twice the amount he managed in his final season at Liverpool.

Alexander-Arnold, meanwhile, has struggled to get going. Madrid paid €10m to release the full-back from his contract early so that he could play at the Club World Cup and being acclimatising to Xabi Alonso's demands as soon as possible. But after an underwhelming summer in the United States, Alexander-Arnold then suffered a hamstring injury in early September that ruled him out for six weeks.

A further muscle injury followed in December that kept him on the sidelines for another two months, by which time Alonso had been sacked while another ex-Liverpool right-back, Alvaro Arbeloa, had been placed in charge.

Alexander-Arnold is now belatedly finding his feet under Arbeloa, who has taken more of a hands-off approach when it comes to tactical configurations than his predecessor. Arbeloa has put faith in youth, and, for the most part, allowed his best players to figure things out for themselves, much like Carlo Ancelotti did before Alonso's short tenure.

For Alexander-Arnold, that has meant learning how to operate with the best in the world on the fly, but he needs regular games to do so. The 27-year-old has played just 754 minutes in La Liga this season, and even though he has provided four assists, including two in his last two games, he still looks an awful lot like a player still settling in at a new club.

This is natural, of course. Alexander-Arnold spent his entire professional career until last summer on Merseyside, where he was a crucial cog in a well-oiled machine. Here, there are fewer guardrails, with Madrid's football more off the cuff. Alexander-Arnold is yet to fully adapt to such an environment.

For Alexander-Arnold, that trust means accepting some of his weaknesses. His defensive issues have long been chronicled - and perhaps a little bit overstated. Alexander-Arnold isn't outwardly a bad defender, but he does have pretty obvious lapses that are then picked over by analysts, both professional and amateur.

At times, Alexander-Arnold still looks very much like what he is, a converted midfielder who was never classically educated on the defensive intensity of being a full-back. It is perhaps only because he is so effective going forward that his issues at the other end are so highly scrutinised.

But that does not mean that they should be excused. During his Liverpool days, teams would routinely exploit the Reds' right flank. Liverpool adjusted accordingly, as both under Klopp and Arne Slot, there would always be a midfielder tucked in behind the Engliushman to offer cover. Sure, Alexander-Arnold was a defensive weakness, but Liverpool, in effect, double-teamed whomever he was tasked with marking.

Madrid haven't afforded him that same luxury, and it's shown up on more than occasion. Alexander-Arnold was tormented by Manchester City's Jeremy Doku in the Champions League and committed a couple of woeful errors against Celta Vigo in La Liga. On Saturday, meanwhile, his late failure to track a runner against Mallorca saw Los Blancos fall to an embarrassing loss that has delivered a significant blow to their title hopes.

The Spanish press have been accordingly merciless, with Marca were pretty damning in their assessment of Alexander-Arnold's defending in that recent loss to Celta: "Anyone who regularly watches Liverpool knows that Trent isn't exactly a defensive hound; his strength lies in pushing forward and distributing the ball with his exquisite passing. But defending? Forget it, as was proven once again with Celta's first goal. The only question is whether he doesn't know how or simply doesn't want to. So if you're a Real Madrid fan, don't get angry with the English full-back if you don't like his defensive performances. If anything, be angry with whoever signed him."

Those recent errors could not have come at a worse time for Alexander-Arnold in terms of his World Cup participation. Tuchel didn't select him for England's friendlies against Uruguay and Japan in March, a decision that divided opinion amongst fans and media. Tuchel brushed off the suggestion that Alexander-Arnold should be an automatic part of his squad, admitting that it was a "tough" decision to leave the right-back out, but insisted he did it for "sporting" reasons. Put bluntly, Tuchel doesn't see the former Liverpool man as an ideal fit for his side.

A lot of those who were angry about the decision don't watch Madrid week in, week out. If they did, they could tell you that Alexander-Arnold isn't in great form. And perhaps those on Alexander-Arnold's side could also look at Tuchel's system and admit that a full-back with a better defensive attributes is far more suited to the vision of football that the German has.

Time is therefore running out for Alexander-Arnold to prove himself worthy of a recall this summer. Performing well up against one of the world's most in-form wingers in a massive Champions League knockout tie would certainly go a long way to helping his case. Be exposed, though, and any hope he had of forcing his way back in could well be over, barring injuries to others in Tuche's thinking.

At the pointy end of the most elite competition in football, individual match-ups are everything. Bayern, no doubt, will have highlighted Madrid's right flank as an area they can surely expose. And of course, the great irony here is that, in Diaz, they have the player perhaps best equipped to play against Alexander-Arnold. One can only imagine the number of times they went up against one another in training; if anyone knows which way to dart and duck around Alexander-Arnold, it's the guy he is going to be marking for 90 minutes.

"I don't want to say that other games are less important, but when there is so much hype around a game and so many eyes on it, you know you have to perform. When you play for a club like this the expectation is that you have to win," Alexander-Arnold said following Madrid's last-16 win over Man City. And while team achievements should always be front of mind, he will be well aware of just how much is on the line for him personally this week.