Henrikh Mkhitaryan, who injured knee ligaments in the first leg of the quarterfinal against CSKA Moscow, will miss the West Ham match but Wenger said it’s “possible” he could be back for the game against Atletico.
Mkhitaryan is running again and will try to step up his training over the coming days, Wenger said.
Pierre-Emerick Aubameyang, who is cup tied in the Europa League, could be rested against West Ham.
Aubameyang has six goals in eight league games since arriving from Borussia Dortmund in January, but Wenger said it may make more sense to play someone who can face Atletico.
“I would say most of the time, after the Europa League games, it was a help [to have him] because I could rest some players and bring someone fresh in,” Wenger said. “When you prepare for the Europa League, it is a handicap because he cannot play, and when the games become important like they are at the moment, it raises the question.”
“For us, it’s absolutely vital to beat them and to have a chance to go into the final and win the competition,” Wenger said. “We have a big obstacle, a big hurdle in the semifinal.
“I would even say that Atletico Madrid are seen as the favourites to win the competition, but I believe that at our best, we can beat them.”
When asked, Wenger also said he is firmly in favour of safe standing, even though the Premier League said on Wednesday that it needs more evidence fans support its implementation before it can make a decision.
“The atmosphere is much better when people stand. The closer you are to the position of the player, the more supportive you are,” he said. “I think as well that it is a tradition of English football to have that, and overall, I must say it is much better.
“There are safety reasons that they don’t do it and I can understand that, but if the safety is right, then it has my 100 percent backing.”