The Wales international was forced off injured inside 16 minutes of his second-half introduction on Tuesday night as Arsenal were 4-0 winners against Hull City in their FA Cup fifth-round replay.
Ramsey sustained a thigh injury but the severity of the Welshman’s problem remains unclear ahead of a vital run of games for the FA Cup holders.
Speaking ahead of Sunday’s quarter-final, Wenger confirmed Ramsey would miss the clash against Watford.
“We lost Ramsey from the Hull game,” Wenger told his pre-match media conference.
Gabriel Paulista and Per Mertescker also picked up injury problems during Arsenal’s costly 4-0 victory over the Tigers.
But Arsenal manager Wenger revealed the centre-halves would be fit to face the Hornets, although he is unsure whether Laurent Koscielny will be risked for the quarter-final tie.
“Gabriel and Mertesacker came off injured but they should be available,” Wenger added.
“Koscielny is not far, I’m not sure if I’ll risk him or not. It could be a little bit of a risk but I haven’t made a decision yet.”
Wenger added that Hector Bellerin would be in the match-day squad, while Francis Coquelin is set to return from suspension after his sending off in last weekend’s north London derby.
“Coquelin is coming back from suspension,” Wenger said.
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