United have the small matter of a clash against rivals Manchester City on Sunday in the Premier League.
But Mourinho believes today's Champions League game with Juventus is so important that he cannot take the team's focus away to a future match.
"(Juve) is a big match and is big enough not to think about what next," said Mourinho during his press conference.
'It is big enough to think about just the match against Juventus.
"It is not a crucial match for us, I think independent of the result, our next matches against Young Boys and Valencia are the matches that are going to define the qualification in second position or who goes to the Europa League.
"There are two more matches to play (after Juve) and we can still qualify so I think we will fight for qualification until the last match.