Rashford was forced off late on during United's 2-1 win over Barcelona, in which he struggled to assert his attacking talents, and following the game posted a cryptic social media message to suggest a fitness concern.
Asked on Friday, a little over 12 hours after the game, for an update on Rashford, manager Erik ten Hag said more tests were needed to confirm the severity of the injury.
He said: "I don't know, the players now are coming in, we have to do investigations, medical of course we did straight after the game, but most of the time you have to wait for a 100 percent diagnosis. So let's do the medical, the work, we have to wait."
He has though been passed fit and starts for United, who are looking to win their first trophy since 2017.
They have no fresh injury concerns with Donny van de Beek, Christian Eriksen and Anthony Martial still out.
Wout Weghorst continues to start up front, while Jadon Sancho, who struggled as a No10 against Barcelona, drops to the bench as Antony comes into the side.
Diogo Dalot gets the nod over Aaron Wan-Bissaka at right-back, while club captain Harry Maguire is once again on the bench.
Man United XI: De Gea, Dalot, Varane, Martinez, Shaw, Fred, Casemiro, Fernandes, Antony, Rashford, Weghorst
Subs: Heaton, Lindelof, Maguire, Wan-Bissaka, Malacia, McTominay, Sabitzer, Garnacho, Sancho