1031 GMT March 31, 2020
The Red Devils were beaten 1-0 by bottom side West Brom at Old Trafford on Sunday, ensuring rival Manchester City won the title, BBC Sport reported.
United plays Bournemouth in the league tonight before facing Spurs.
"The way you play is the only way I can select players," said Mourinho.
The Portuguese manager said "some of the guys" that played against West Brom "don't have a place" in the team for the semifinal at Wembley.
He added the Bournemouth match at Vitality Stadium was "an opportunity for some people to play and to try to get a place in the team for Spurs".
When asked to clarify if he meant those who performed badly against the Baggies will now not face Spurs, Mourinho said, "Yeah.
"What is the criteria for a manager to choose a team?
"I only know one criteria: is the way you play.
"Or do you want me to go for the price they cost, or their salary, or their beautiful face? The only way is to go with performance."
United midfielder Ander Herrera was taken off at half-time against West Brom, while Paul Pogba was replaced in the 58th minute.
Regarding Pogba's performance, Mourinho said, "It was not just him and he had a yellow card, so he was in a more difficult position than others.
"And playing with only two midfield players, you cannot play with one player in risk of not being able to make a foul.
"You can do it if your team is not losing the ball, but our team was losing the ball so easy with the complication, everything was complicated, so we were losing lots of balls.
"Paul was out because of the yellow card, because of in terms the way he played he was not worse than some others that were on the pitch for 90 minutes."