Ruben Amorim has been dealt another blow after confirming Diogo Dalot could miss the rest of the season with a calf injury.
Dalot has only missed one of Manchester United's games this season, when he was suspended for the 3-1 win over Southampton in January.
But he will be absent for Sunday's trip to Bournemouth in the Premier League and, according to Amorim, could sit out the rest of the season.
"Diogo Dalot is out," Amorim told a news conference on Friday. "We don't know how long he's going to be out. But he's out for these next games. We will see to the end.
"There is that possibility [he could miss the rest of the season] but I don't know, we will check week by week."
Amorim is set to rotate his squad at the Vitality Stadium ahead of the Europa League semifinal first leg against Athletic Club in Spain on Thursday.
He's hopeful of having Matthijs de Ligt and Amad Diallo available soon after injury lay-offs, but Dalot's absence represents a major problem after being close to ever-present this season.
"There is that possibility [that he could miss the rest of the season] but I don't know," said Amorim.
"We will check week by week because he works really hard. He can recover quite well, we'll see. He has something in his muscle, his calf.
"He had a sequence of games, he played all the time. We try to manage it but the players play a lot of minutes and are not so ready to cope with that."
Despite focusing on the Europa League, United need Premier League points to finish as high up the table as possible.
They could yet finish 17th with West Ham, who occupy the place above the relegation zone, are just two points behind.
"We are going to face this game [against Bournemouth] with the best team," said Amorim.
"We had a full week to prepare. Some of the players didn't play against Wolves so recovering the players is not a bad thing. I will try to prepare for this game and try to win the next one."
