Nowhere has the Arsenal rebuild under Mikel Arteta been felt so severely as in defence.
When the Spaniard arrived in December 2019, he inherited a squad with the likes of Sokartis, David Luiz, Hector Bellerin and Sead Kolasinac.
Now, just over two years later, all have been shipped out, as have Pablo Mari, Shkodran Mustafi and Calum Chambers.
The overhaul has been dramatic, with Kieran Tierney the only defender at the club when Arteta arrived who is still considered as a guaranteed starter in the new-look back four.
The defensive shake-up started almost as soon as Arteta was appointed, with Mari and Cedric Soares being brought in during the 2020 January transfer window and Gabriel Magalhaes joining from Lille prior to the start of Arteta’s first full season in charge.
However, it wasn’t until last summer when it really kicked into overdrive, with Ben White, Takehiro Tomiyasu and Nuno Tavares arriving, as well as Aaron Ramsdale, who almost immediately established himself as first-choice goalkeeper.
In all, Arsenal have signed seven senior defenders since Arteta was appointed. Interestingly, they have picked up four midfielders during the same time frame but have yet to bring in a single attacker.
In Tomiyasu, White, Gabriel and Tierney, Arsenal have built a settled back four – all of whom are 24 or younger.
It’s a defensive unit which Arteta believes he could build his team around for years.
“The potential [to do that] is there,” the Arsenal boss said. “It’s because of the qualities they have individually, how they can complement each other with those qualities and, obviously, because of the age group.
“If we manage them well and they are willing to sustain that, they have a really bright future.”
Arsenal have conceded 25 goals in their 21 league games so far this season, but nine of those came in the opening three games – before Tomiyasu was signed, while Gabriel and White were absent due to injury and Covid-19 respectively, and before Ramsdale had replaced Bernd Leno in goal.
From the moment the new back four first played together, during the 1-0 win against Norwich on September 11, they have let in just 14 goals in 20 Premier League games – keeping 10 clean sheets in the process.
There is no doubt Arsenal now have a more solid base at the back and with Tavares proving to be a very able understudy to Tierney at times, they have added depth to the left-back position.
The focus this summer will be finding cover for Tomiyasu – with Middlesbrough’s Djed Spence a target – and then integrating William Saliba into the squad for the first time since his £27 million ($34m) switch to Arsenal from Saint Etienne in July, 2019.
Saliba, of course, has yet to play a single competitive game for Arsenal since his move from France, with the Gunners sending him back on loan to Saint-Etienne for the 2019-20 season.
The 20-year-old then had a spell with Nice during the second half of the following campaign and is currently with Marseille, where he has been producing consistently impressive performances under the guidance of coach Jorge Sampaoli.
Saliba has made 21 appearances in Ligue 1 this season and appears to have a game that is perfectly suited to Arteta’s way of thinking.
He is good on the ball, averaging 82.8 passes per 90 minutes – that’s far higher than White (52.8), Gabriel (57.5) and Rob Holding (52.2).
His passing accuracy of 93.5 per cent also puts him clear of all three of Arsenal’s current centre-backs, as does his possession loss rate – which is just 8%.
Saliba also reads the game well. He averages 1.2 interceptions per game – only White (1.4) averages more – And he wins possession 7.1 times per 90 minutes, which is significantly higher than White (5.2), Gabriel (4.1) or Holding (4.9).
It must be noted, of course, that Saliba is playing in Ligue 1 rather than the Premier League, but even so, those numbers are very impressive for a centre-back who does not turn 21 until March.
Arsenal have been monitoring his performances closely, with loan manager Ben Knapper and technical director Edu flying out to France to watch him in action several times throughout the season.
And although there have been suggestions in the French media that Saliba would be open to remaining with Marseille on a permanent basis, Arsenal continue to insist that he remains a key part of their future.
There has been some strong criticism at the way Arteta has handled Saliba, with many fans left baffled that a player who was bought for such a high price has still to make his competitive debut three years after joining.
But Arsenal believe his development in France shows that they were right to manage him the way they have, as it has allowed the defender to play regularly at a young age away from the relentless spotlight of the Premier League.
And Saliba has clearly flourished at Marseille, drawing widespread praise – with former Arsenal forward Stephy Mavididi, who currently plays for Montpellier, labelling him as one of the best centre-backs he’s ever come up against.
"That guy's a player," Mavididi said during a recent interview with LiveScore. “He's hands down one of the best defenders in the league.
“I think he'll walk back into the Arsenal team next season. He's strong, good on the ball, he reads the game well. He's one of the best centre-backs I've faced.
“Everyone can talk about Marquinhos, Thiago Silva, Jerome Boateng, but he's up there. He's the one that surprised me the most.
“I’m an Arsenal fan, too, and playing against Saliba I thought, 'We've got a very decent defender here.'"
The key thing when it comes to Saliba this summer is convincing him that he is an integral part of Arteta’s plans.
Understandably, he and his representatives are unsure where he figures in the Spaniard’s thinking and that will be a crucial question that needs answering during planned talks this summer, which are expected to include discussions over a new contract.
However, Arsenal will point to the fact that there is now a clear space in the squad for Saliba to come in and compete with White and Gabriel for the two centre-back spots next season.
It’s been a long time coming, but a clear pathway is now opening up for the young Frenchman at Arsenal. Whether he decides to use it, that'll be for him to decide at the end of the season.
If he does, though, he could prove the final piece of Arteta’s defensive jigsaw.