LONDON -- Arsene Wenger says Olivier Giroud could miss the next three weeks with a hamstring injury, which will likely put more pressure on Arsenal's squad going into the congested holiday period.

Giroud limped off during Tuesday's 1-0 win over West Ham in the Carabao Cup and Wenger said he will miss Friday's key Premier League game against Liverpool -- and probably longer.

"It looks like that [21 days]. We have to wait, normally nowadays you do the scan 48 hours after the injury, so that will happen on Thursday. Then we have a precise idea of what kind of grade his hamstring is," Wenger told a news conference. "When you listen to him, the pain is quite big. But the grade is not always linked with the intensity of the pain."

Arsenal advanced to the semifinals with Tuesday's win, courtesy of Danny Welbeck's first-half goal, which adds another two games to an already busy January. In total, Arsenal now face 12 matches between Friday and Feb. 3, and will be without their backup striker for much of that period.

"It is very demanding, especially because we have already a tough schedule behind us. I will have to sit down and analyse very well what we can do," Wenger said. "But what is very worrying in my job is when you start to lose players, like Giroud tonight. After you cannot afford to lose another one.

"So I have to look how I can manage the schedule. It puts more pressure on the rest of the squad. But I still have Theo Walcott, Danny Welbeck can play up front, [Alexis] Sanchez can play up front. So that's a possibility as well."

The Carabao Cup -- traditionally known as the League Cup -- is the only domestic trophy Wenger has yet to win, but he indicated he will continue to rotate heavily even for the semifinals. He made 11 changes from Saturday's 1-0 win over Newcastle for Tuesday's game.

"When you look at our fixtures in January now, and February, you cannot imagine that you play with always the same players in every single game," Wenger said. "Will I change from Premier League game to Premier League game, or only in the Carabao Cup, I don't know yet. I have to look at the fixtures to see what I do."

West Ham have enjoyed a recent resurgence under David Moyes, including a 0-0 home draw against Arsenal in the league last week, but were toothless here.

They had just one shot off target as Moyes himself made six changes, with the former Manchester United boss left frustrated with the overall display.

"I think we are making steady progress but I was disappointed with the quality of our play,'' he said.

"Overall, we were never out of the game in a cup match against Arsenal. We have conceded one goal in two games against them now and I think if you said that the day I arrived here I would have taken that.

"We put out a strong team, what was available to us but we have got big games coming up as well and arguably, I am in a more difficult position than Arsene Wenger.''

Moyes was unable to select Manuel Lanzini after he was hit with a two-match ban following a retrospective charge for diving to win a penalty at Stoke.

"I am disappointed because I don't see any consistency,'' added Moyes.

"I'm not sure even in this room, everybody would be unanimous and that was what it said it had to be.''

Press Association contributed to this report.