Jose Mourinho discusses Manchester United's injury crisis
Manchester United have the Europa League semi-final first leg against Celta Vigo on Thursday.
So Mourinho has made four changes to the starting XI to try and keep his players fresh.
Captain Wayne Rooney has come in, as have Luke Shaw, Ashley Young and Jesse Lingard.
"We are rotating players," he said on BT Sport.
BT SPORT
Jose Mourinho has made some changes for Man United's game with Swansea
Rooney, Ashley Young, Lingard, and Luke Shaw didn't play the last match
Jose Mourinho on Man United's team v Swansea
"We are trying to rotate. We don't have many to do it.
"Rooney, Ashley Young, Lingard, and Luke Shaw didn't play the last match.
"We have four fresh players to try and compensate the fatigue of some others."
Juan Mata is named on the bench after missing eight games through injury and youngsters Axel Tuanzebe and Scott McTominay are also among the substitutes.
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BT SPORT
Jose Mourinho is pleased to see Juan Mata back on the Man United bench
"Axel is already four, five, six matches on the bench with us," Mourinho added.
"Scott is the fist time. For them it's a good experience.
"Even if they are not on the pitch it is always a good experience. We try to get the kids we think are better to give us a hand.
"We need everyone, Mata is coming back. It's a good effort to be back as soon as possible. Paul (Pogba) will be ready for the next match. We fight with everything we have."