The Red Devils were beaten 0-2 at Old Trafford for the fifth time in six Premier League games as Jean Philippe-Mateta struck twice for the Eagles in the second half, either side of a lengthy stoppage for Martinez to receive treatment.
"Licha is really important for us, not just as a football player but the character he has, especially in this hard moment," said Amorim. "Now it's time for us to help Licha. I think it's a bad situation. Let's wait to assess things with the doctor, but I think it's a serious situation."
But the Portuguese coach insisted United must learn from their mistakes of the past in the transfer market and not be panicked into making costly deals. "We are trying everything to improve the team without doing mistakes of the past, and trying to balance the urgency of the moment," added Amorim.