Rashford, our Man of the Match in the 3-2 victory over Liverpool in the Emirates FA Cup fourth round, was hurt during the second half.
“Marcus felt his knee but we'll have to do a scan,” manager Ole Gunnar Solskjaer revealed. “Hopefully, it's not too bad but we'll see tomorrow.”
The England international scored twice in the last meeting between the clubs, when the Reds won 3-2 at Bramall Lane before Christmas, and Ole could provide another update in his press conference on Tuesday afternoon.
Meanwhile, Eric Bailly should be an option for one of the centre-back slots after missing the FA Cup tie.