Bowen is the Hammers' top scorer this season with 19 goals in 40 appearances across all competitions, including a strike in last month's 5-0 second-leg win over Bundesliga outfit Freiburg in the last 16.
The 27-year-old England international was handed a start up front for West Ham in last weekend's 2-1 victory at Wolverhampton Wanderers in the Premier League.
However, Bowen limped off down the tunnel just nine minutes after the interval following a strong collision with Wolves midfielder Mario Lemina.
Moyes and his West Ham squad arrived in Germany on Wednesday evening ahead of their encounter with Bundesliga champions-elect Leverkusen at the BayArena on Thursday, but Bowen has not travelled with his teammates and remains at home in recovery.
Bowen ruled out of Leverkusen clashMoyes has admitted that Bowen's absence will be felt by West Ham, but the Scotsman is confident that he has other attacking options at his disposal who can step up on Thursday.
«Jarrod's not with us. He's got an injury and he's not available to play tomorrow night. We're not sure about when he might return at the moment,» Moyes said at a press conference on Wednesday.
«We think [when he got the knee in his back] he's twisted and he's probably damaged a bit of something, a bit like a fast bowler gets in cricket. It's about the rotation, which is where we think the damage has come from.
»Jarrod will always be a miss because he's a boy who's played a big part in memorable games for us, especially in the UEFA Europa Conference League final last year.
«But, these
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