United could be without Anthony Martial against West Ham on Tuesday night.
The 20-year-old Frenchman limped out of the warm up before the 1-0 win at Norwich at the weekend with a tight hamstring and is now a doubt for the Upton Park trip.
It would be a blow: we need to win our final two games of the season to be sure of a place in the top four and a place in next season's Champions League.
It will be a difficult enough task for Louis van Gaal's side but there are plenty of options if Martial isn't passed fit.
Martial has been playing on the left of a front three but would have played as the striker at Carrow Road if he hadn't pulled up in the warm up.
Memphis got the nod on the left wing but didn't take his chance.
He'll be lucky to keep his place but he remains the most natural choice.
When Martial missed the matches against Midtjylland and Arsenal in February, the 22-year-old filled in on the left and had two good games.
Adnan Januzaj hasn't played for the first team since coming as a late sub in that match against the Gunners.
He played 45 minutes for the Under 21s on Friday and was on the bench at Norwich less than 24 hours later.
He would have come on if Van Gaal hadn't- bizarrely- changed his mind twice.
He played as the no.10 when he was in the team in August but has played largely on the left plenty of times before.
However, Van Gaal did hint after the weekend win that Januzaj was not fit enough to start in Martial's absence having made only two substitute appearances since returning from his loan spell at Borussia Dortmund.
Marcus Rashford was rested at Norwich but should return to the team at Upton Park.
Van Gaal has flirted with playing the 18 year old wide and he's done the job for the Under 21s this season.
It remains as a striker that he's had the biggest impact.
It's possible that Van Gaal will move Rashford to the left and play Wayne Rooney up front with Ander Herrera keeping his place in midfield.
It would give LVG the pace he wants in the wide positions and Rooney scored seven in nine as the main centre forward before his knee injury in January.
How United could line up at Upton Park in the possible absence of Tony Martial