Manchester United played Leeds twice in a rare double-header Premier League fixture last week and they secured four points from those two fixtures. Both performances weren't vintage but Sunday's win at Elland Road was a crucial victory.
But what did Erik ten Hag learn from those matches? It seems he would have been sent a reminder about who his most valued defender is, as he was named on the bench to play Leeds at the weekend and his absence from the team was obvious.
Lisandro Martinez was rested on Sunday ahead of Thursday's match against Barcelona at Camp Nou, even though it's a fixture which he's unavailable for due to picking up three yellow cards in the Europa League group stage.
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Although United recorded a clean sheet against Leeds at Elland Road, that looked unlikely for large periods of the game. David de Gea made a couple of key interventions and the hosts, who are struggling in the league, should have found the net.
Luke Shaw and Harry Maguire were the preferred centre-back pairing for the match and the latter highlighted why Martinez was signed for £46.8million, rising to £55.3m, in the summer and why his own days at Old Trafford are numbered.
Maguire, perhaps unnerved by the hostile atmosphere, was awful with the ball throughout the contest. His passing was sloppy, wayward and unconvincing, which meant the build-up play was affected and uncharacteristically poor.
United won the match 2-0 thanks to brilliance from Marcus Rashford and Alejandro Garnacho, but they could not leave their own half for portions of the first 45 minutes, particularly, in which Leeds pressed well and Maguire struggled to consistently find a pass.
Whilst the England international's limitations are no secret, his passing is usually a strength and yet it let him down against Leeds. It had a knock-on effect on the midfield and it showed just how important Martinez is to the dressing room.
The Ajax supporters who adored Martinez during his time in Amsterdam highlighted his personality and his passing ability as his most endearing qualities ahead of his move to Manchester and that has been seen during his time at the club.
The centre-back is already a fan favourite and his passing ability is instrumental to how Ten Hag wants to play. Martinez is confident on the ball and he's able to break the lines with his dynamic range of passing, which is crucial to build-up play.
Without him in the starting lineup at Elland Road, the team looked dysfunctional at times, as he was not there to orchestrate from the back and it does not seem a coincidence United scored twice after he was substituted onto the pitch.
However, Maguire was not the only player to pay a compliment to Martinez over those four days, in which two games against Leeds were played, because the limitations of Raphael Varane's playing ability were also exposed last Wednesday.
Leeds shocked Old Trafford with a goal through Wilfried Gnonto almost immediately after the first whistle last week and that was achieved by forcing United into losing possession, which Varane more than played his part in.
The Frenchman received the ball three times at the very start of the game and on each occasion, he passed sideways or backward, which invited pressure from Leeds. Varane is a world-class defender but he's not perfect.
When analysing the defensive options, Martinez is undoubtedly the most competent passer of the ball and the importance of that quality to build-up play can't be understated, as he bridges the gap between the backline, midfield and attack.
Martinez has averaged an impressive 0.59 key passes per 90 in the Premier League this season, whereas Maguire has averaged 0.21 and Varane 0.06, which confirms the visual impression the three centre-backs have given.
Against a Barcelona side that is famous for prioritising possession, his passing ability will be a colossal miss for United.
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