David Moyes says he does not know how long Jarrod Bowen’s back injury will keep him out, raising fears West Ham may be without their top scorer for the entirety of their Europa League quarter-final tie against Bayer Leverkusen.

Bowen has not travelled to Germany for Thursday night’s first leg after being forced off during the second half of Saturday’s 2-1 Premier League victory over Wolves, with Kalvin Phillips also missing the trip through injury.

In the immediate aftermath of that game, Moyes expressed hope that Bowen’s problem was “not too bad”. But speaking in Leverkusen on Wednesday evening, the Scot painted a less optimistic picture.

“Jarrod’s not with us, he’s got an injury and he’s not available to play tomorrow night,” he said. “We’re not sure [on a timeframe] and I probably wouldn’t be giving any dates of when we’ll get him back. I couldn’t give that at the moment.”

Bowen has been in superb form for the Hammers this year, scoring 19 times in all competitions, and his absence at the BayArena is a major blow to Moyes, who is trying to plot the home side’s first defeat in 42 matches this season.

Bowen was injured in a collision with Wolves’s Mario Lemina and after briefly attempting to continue was replaced by Aaron Cresswell at Molineux.

“We think that when he got the knee, he’s twisted and damaged a bit of something,” Moyes explained. “They said it’s like what a fast bowler gets, with the rotation. We think that’s where the damage has come.”

The West Ham squad for Thursday night’s contest suddenly looks thin, with goalkeeper Alphonse Areola still out with a groin strain and Edson Alvarez suspended.

Phillips is also absent after picking up a fresh issue in training on Tuesday as his desperate loan spell continues.

“He kicked the back of one of the boys’ legs and we think he’s just tweaked a bit of his lower hamstring at the back of his knee,” Moyes added. “I don’t think it’s long-term but it only happened yesterday so I’m not quite sure.”