How do you improve the best defence in the Premier League? That was the question facing Arsenal manager Mikel Arteta as he headed into this summer.
For each of the last two seasons, Arsenal have had easily the best defensive record, conceding at least 15 goals fewer than any other team (63).
It’s not really the most obvious area to try and improve, then, is it? But Arsenal finished second in both of those seasons and the one before that, and haven’t won a single trophy in that time. Eight other Premier League teams have won something of note in that period.
One problem – if that’s what you can call it – in Arsenal’s defence is that the drop-off in quality from the first-choice centre-backs to the second string is too great. That’s always going to be a bit of an issue when you have two of the world’s best defenders in William Saliba and Gabriel Magalhães as the main pair in those positions, particularly given they make an even better partnership. They will play every big game that they are available for, so whenever they aren’t able to play, Arsenal feel the effects of bringing in an undercooked back-up who just isn’t as good.
In 2022-23, their title tilt fell apart when Saliba was injured for the run-in, and in 2024-25, Gabriel missed the last couple of months of the campaign. Although Jakub Kiwior did well enough as his stand-in, there’s no doubt Arsenal would have been better off with the Brazilian – in attack as well as in defence. In the 13 Premier League and Champions League games Arsenal played in 2024-25 as they fell away in the title race and were knocked out of Europe after Gabriel got injured, Arsenal only scored goals from corner situations against relegated sides, Ipswich Town and Southampton. They had scored 11 goals from corners in 39 games before then.
Coming into this summer, it was clear Arsenal weren’t going to improve on those two. So, they’ve decided to go out and sign one of the most promising centre-backs in Europe in the shape of Cristhian Mosquera, who has only just turned 21 but already has two full seasons of top-level football under his belt. And he can play on either side of central defence, as well as at right-back. So, not only is he one for the future, he is also being brought in to allow Arteta to rotate Arsenal’s first-choice defenders more throughout the season, reducing the chances of them picking up season-derailing injuries.
Mosquera came through the youth ranks at Valencia before making his first-team debut in early 2022, aged just 17. He made only four starts and five substitute appearances in La Liga over the next 18 months, but then properly broke through at the start of the 2023-24 season. Since, he has been one of the most consistently present players in Europe, and he has played more football than anyone else in his age group.
In Europe’s top five leagues in the last two years, Mosquera has made more starts (70), racked up more appearances (73) and played more minutes (6,394) while under 21 years old than any other player. In that time, he’s made 11 more league appearances than Désiré Doué, started 15 more games than Savinho while under the age of 21, and played over 1,300 more minutes than Lamine Yamal. He’s got a lot of game time under his belt for his age.
In total in his career, Mosquera has made 74 La Liga starts; the last player to have started as many games before turning 21 years old was Aymeric Laporte in April 2015. The previous player to achieve the feat was César Azpilicueta in December 2009, and the only one to manage it since Mosquera is Barcelona’s Gavi in February 2025. In terms of La Liga game time at a young age, Mosquera is in good company.
In his first season in the first team, he played mostly on the right side of a back four, forming a formidable partnership at the back with former Arsenal man Gabriel Paulista, before the Brazilian was sold to Atlético Madrid in the winter transfer window. And who was behind that drive to sign Gabriel Paulista? The then-Atlético and now-Arsenal sporting director, Andrea Berta. He clearly liked what he saw from that Valencia defence.
But that move didn’t work out. Gabriel Paulista left for Besiktas on a free transfer at the end of the season. Fast forward 12 months, and Berta is now attempting to sign the other half of that partnership at a different club.
Perhaps he was further impressed by how Mosquera continued to improve, not least in how he adjusted without his defensive partner last season. Mosquera moved over to left centre-back without issue to allow the inexperienced César Tárrega to play in his favoured right centre-back position, also playing a few games in the middle of a back three and even filling in on a handful of occasions at right-back.
He started 37 of 38 games and played 90 minutes in all but one of his appearances. In those two seasons in Valencia’s first team, he didn’t miss a single game through injury. The only one he missed was due to suspension, and Valencia fell apart without him, losing 7-1 at Barcelona. Obviously the quality of the opposition made a bigger difference than Mosquera’s absence, but it’s still noteworthy that they conceded 13.0% of their total for the season in that one game he missed.
So, what does he add when he plays?
At 6-foot-2, he is a significant presence, and although he doesn’t do well in aerial battles, owning one of the worst aerial duel success rates among centre-backs in La Liga last season (51.4%), he is among the best in the league when it comes to dealing with an opponent dribbling at him.
‘True’ tackle attempts is a sum of successful tackles (where possession is regained or when the ball goes out of play and is safe), challenges lost (where a player attempts a tackle and doesn’t connect with the ball) and fouls when attempting a tackle. We can use true tackle success rate – the proportion of true tackles that are successful tackles – to get an idea of how good players are when defending against dribbling. It turns out Mosquera is pretty good at the defending part of being a defender.
Of all 195 players to attempt 50+ true tackles in La Liga last season, Mosquera had the highest success rate (76.7%), proving just how adept he is when it comes to one-on-one defending. In the Premier League, Saliba ranked second for true tackle success rate (79.5%) behind Nottingham Forest‘s Nikola Milenkovic (81.0%).
Arteta likes defenders who thrive in duels and don’t get beaten often, and Mosquera fits the bill on that front.
He is also comfortable on the ball. In his first full season in La Liga, he completed 88.6% of his passes, and that rate rose to 91.2% last season. He was the only La Liga player in the top 20 for pass success rate who played for a team outside the top seven for possession in 2024-25. That is, he played for a team who prioritised keeping the ball less than anyone else in the top 20.
He is a little cautious with his passing, though. He ranked 11th in La Liga for total passes attempted, with 2,048, but just 3.8% of them were classed as ‘progressive’ – a successful open-play pass in the attacking two-thirds of the pitch that moves the ball at least 25% closer to the opposition’s goal. Only three other players in the top 20 for passes attempted fared worse for the proportion of them that were progressive. Meanwhile, it is illustrative of how short and safe he kept his passes that not even one of his 2,048 passes created a chance for a teammate.
He does more of his best work with the ball by bringing it out of defence, with only six defenders, all of whom play for more possession-dominant teams, recording more ball carries (503) or more progressive ball carries (moving at least five metres towards the opposition’s goal) than him (286).
Still just 21, he isn’t a complete defender. His passing isn’t at the elite level of someone like Saliba, and he isn’t the best in the air either, but these are elements of his game that can be improved. Training alongside better players will only increase the chances of that happening.
But Arsenal do appear to be picking up a gem in Mosquera. The only question is whether he is too good not to be playing regularly, and that could mean there is a degree of pressure on the starting centre-backs that has been absent for the last three years.
Maybe, just maybe, that could mean the Premier League’s best defence gets even better.
