Jarrod Bowen will miss the first leg of West Ham’s Europa League quarter-final against Bayer Leverkusen on Thursday because of a knee injury.
The forward, who has scored 19 goals this season, sustained the injury against Wolves on Saturday and might also miss the return leg on 18 April.
“Jarrod isn’t with us. He’s twisted his knee and there’s some sort of damage,” said Hammers boss David Moyes.
“We can’t give any dates of when he might be back, unfortunately.”
Bowen came off after 54 minutes during the win at Wolves and has been a key player for West Ham this season.
“He’s an England international and we know how important he is to our team, so he’ll be a miss for sure. But we have good players who can come in, so we’ll stay positive,” added Moyes.
West Ham midfielder Edson Alvarez is suspended, while midfielder Kalvin Phillips and goalkeeper Alphonse Areola will also be absent through injury for the game against Bundesliga leaders Leverkusen.
“I see it as a great opportunity,” said Moyes. “We’ve had a good run in Europe and played a lot of good teams, and we play another one.
“Hopefully, we can rise to the challenge and perform well. Both teams have 11 players, so it’s an even game at the start.
“We know Leverkusen are a very good team, but we believe in our abilities.”
Leverkusen have a 16-point lead in the Bundesliga with six games to go, and are unbeaten in all 41 matches this season in all competitions.
“It could be the toughest challenge yet. They haven’t lost for a long time, and we know how well they have played this season,” said West Ham defender Kurt Zouma.
“But we are still confident. We know the qualities we have and we showed that against Freiburg in the last round.
“We always play to win. We know we might be missing some key players, but we have a good squad and we’ll all give 100%.”
Leverkusen manager Xabi Alonso was linked with replacing Jurgen Klopp as Liverpool boss but recently confirmed he would be staying at the German club.
“We know what West Ham can do. They have experience in Europe – last season they were champions of the Conference League,” said Alonso.
“We want to go further and starting tomorrow and then next week in London, we have to play to our own game. We are ready.”