The 25-year-old forward has been in sparkling form this season and helped the Red Devils beat Barcelona in the Europa League knockout play-off round on Thursday.
United won 2-1 at Old Trafford to seal a 4-3 victory over the Spanish league leaders on aggregate.
Rashford was substituted in the 88th minute and appeared to hint on Instagram he had picked up a knock, posting an image of himself walking down the touchline looking in discomfort accompanied with a bandaged emoji.
Asked if the forward would be available for the match at Wembley on Sunday, Ten Hag said: "I don't know. So, players now are coming in. We have to do investigations, medical of course.
"Yesterday we did but so straight after the game most of the time you can't say. We have to wait for a 100 per cent diagnosis, so we have to wait."
Ten Hag confirmed Anthony Martial, who has not played since February 1st, will not be available for the match as United attempt to end their six-year trophy drought.
