Luke Shaw, Scott McTominay and Bruno Fernandes were all in training on Monday morning, providing a real boost heading into a difficult assignment against the reigning La Liga champions.
However, there is still some doubt around left-back Shaw's involvement on the night.
With the tie delicately balanced at 1-1, after Joao Felix's opener and Anthony Elanga's equaliser at the Wanda Metropolitano, things will be decided by extra-time or a penalty shoot-out if the sides cannot be separated with the away-goals rule no longer in operation.
Speaking at the pre-match press conference, the boss explained: "As it is right now, we have all the players available for the game tomorrow.