The sight of Raphael Varane fighting back the tears as he trudged his way back towards the tunnel during Manchester United's 1-1 draw with Chelsea at Stamford Bridge on Saturday evening was one of deep concern.
The Frenchman was forced off on the hour mark and replaced by Victor Lindelof after stretching for the ball in an attempt to try and rob it off the toes of Pierre-Emerick Aubameyang. Varane landed awkwardly and his decision to bury his head inside his shirt, all while staring at nothing more than the Stamford Bridge turf, told its own story.
A L'Equipe report on Sunday suggested Varane may be sidelined for three weeks, keeping him in with a shout of making France's World Cup squad, but still ruling him out for United until the resumption of the domestic season on Boxing Day.
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Saturday's stalemate with Chelsea, which saw Casemiro head home a last-gasp leveller for United, was Varane's eighth start of the campaign in the league. He arrived at Old Trafford in August last year considered as one of the best centre-backs in the world and it has not been until recently that United's supporters have seen exactly why he sported that particular tag.
He was regularly in and out of the team last season, suffering a catalogue of injury problems. His longest sequence of Premier League starts last term stood at just six matches, highlighting just how unfortunate he was.
As well as that, Varane was not helped last season by the fact he was playing alongside an under-performing Harry Maguire. The United captain's confidence was already shot to pieces and it was clear that the Reds, if they were to get the best out of Varane, needed to find a better partner for him.
Step forward Lisandro Martinez. The Argentine, who worked with Ten Hag at Ajax, was identified by the latter as the centre-back he wanted to add some steel and grit to United's backline. He arrived at Old Trafford in July for a sizeable price tag and questions were raised about whether the Reds had paid over the odds.
After the 4-0 battering at Brentford ten weeks ago, it appeared as though they had. The Argentine, who will have aspirations of helping his country at the upcoming World Cup, was beaten up and spat back out by Brentford's physical forwards, leaving him to withstand a tonne of criticism and unsavoury comments.
However, just as it was in United's season as a collective, the Brentford horror show was a turning point in Martinez's Reds career. Nine days later, facing the challenge of trying to stop Liverpool and Mohamed Salah, the former Ajax man was paired with Varane in the heart of the defence for the very first time. Neither he or United have looked back since.
The duo, over the last two and a bit months, have formed a promising partnership, complementing each other with their own qualities. Martinez, a ball-carrying centre-back who likes to stride forward and pick a pass, has flourished with Varane by his side, producing a series of eye-catching and encouraging performances.
His game has rapidly improved and he has shown why Ten Hag went against the advice of United's recruitment department, who wanted to sign Pau Torres from Villarreal, to be reunited with the Argentine. However, United and Ten Hag are about to discover just how good Martinez really is without Varane by his side.
The 24-year-old has played the bulk of his football in United colours so far with Varane as his mentor. However, he has, in flashes, played alongside Lindelof, who replaced Varane against Manchester City and Chelsea.
Lindelof, with all due respect, is not at the same level as Varane, though, to his credit, he has been solid and effective when called upon so far this season. But the bond that has developed between Martinez and Varane has been at the very heart of United's recent progress.
The Argentine must now prove that he is capable of continuing at the exact same level without Varane to bounce off.
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