The Frenchman picked up a knock to his left foot during the international clash with England, leaving Louis van Gaal fearing a potential spell on the sidelines for his star man

There were hearts in mouths all across Manchester United's fan base on Tuesday when the sight of Anthony Martial leaving Wembley on crutches was broadcast across the globe.

The striker left the field in the 67th minute of France's international friendly against England, shortly after picking up a knock to his foot which left him limping around for a few moments before his withdrawal. Although he appeared to have shaken off the injury by the time he was pulled for Antoine Griezmann, Martial appeared unable to put any weight on his left foot as he exited the stadium with his team-mates.

The 19-year-old's fitness will be a key concern for United fans ahead of their Premier League trip to Watford on Saturday. Martial has been such a major figure for the Red Devils of late and it would most certainly prove a big blow if the former Monaco man was not available for selection.

So how will Louis van Gaal cope if he is shorn of his star forward? What can United do to cover for the loss of Martial should he be forced to sit out a number of games?

The most likely change would be for Wayne Rooney to be pushed back into the main striker's position which he has filled for much of the season so far. The England captain has netted five goals in 11 games starting as the No.9 this term, but three of those came in the Champions League play-off away to Club Brugge and the other two were scored in otherwise underwhelming performances against Sunderland and Everton.

However, the promotion of Rooney into the spearhead role would allow for Ander Herrera to slot in at the centre of the attacking midfield triumvirate where he has played regularly under Van Gaal. Such a move would allow the Dutchman to continue with Juan Mata and Jesse Lingard on the flanks.

There is, of course, another option waiting in the wings in the shape of Memphis Depay. The £22.3 million man has struggled for game time in recent weeks after enduring a tough start to the season, with performances for both club and country leading to serious question marks over his ability to succeed at the very top level. However, Van Gaal is unlikely to wash his hands of the explosive winger so easily, and any absence of Martial would open a potential window for Depay to come back into the reckoning at Old Trafford.

Such a move could also pave the way for Mata to finally be given a run in the No.10 position after three months spent out on the right-hand side. The Spaniard has often looked to be out on a limb coming from the wide position, with his qualities somewhat nullified by a lack of involvement. A return to the central spot would allow Mata the opportunity to prove his worth as the dictator of United's attack, and may well give the side a whole new angle going forward.

One less likely scenario is a potential return to the lineup for James Wilson. The young striker has himself been struggling with injury of late, with the knock he picked up in the League Cup penalty defeat to Middlesbrough having sidelined him for the last few weeks.

Yet there could be a way back into the limelight for Wilson if he can shake off his own ailment, with Van Gaal potentially open to giving him a rare opportunity in the striker's spot. Marouane Fellaini might be considered to be another option after Van Gaal insisted earlier this season that the Belgian could fill the No.9 position, with Wayne Rooney given time to flourish in the advanced No.10 spot he has occupied in the last couple of club matches.