Roger Schmidt will be without Karim Bellarabi for at least a couple of months after it was confirmed the Bayer Leverkusen winger required an operation on a groin injury.
Bellarabi sustained the injury in the early stages of Saturday's 3-1 Bundesliga win over Hamburg, and was replaced by Julian Brandt.
Leverkusen host CSKA Moscow in their Champions League Group E opener on Wednesday, and head coach Schmidt revealed the bad news in his media conference.
"Karim Bellarabi will be out for a couple of months and will undergo an operation in Basel tomorrow," he said.
"Vladlen Yurchenko has a fractured leg and Kevin Volland isn't quite up to full speed yet. He's fit enough to make the squad, but we'll have to wait and see on that one."
Saturday saw a stunning match-winning cameo from Joel Pohjanpalo. In just his second Leverkusen appearance, the Finn came off the bench with under 20 minutes remaining and scored a hat-trick to turn the game in his side's favour, taking his tally to four in two games.
Schmidt was reluctant to reveal whether the 22-year-old would feature from the start on Wednesday, while providing a word of caution on their Russian visitors.
"Joel has been superb lately and showed on Saturday how strong he is in the box," Schmidt said. "Whether he'll start tomorrow remains to be seen, but he's definitely in contention.
"If you get the better of the likes of Zenit in the league, you must be a good team. CSKA have shown recently how difficult they are to beat. I think the Hamburg win was superb preparation for tomorrow's game, and I hope we can pick up where we left off on Saturday."
Captain Lars Bender sat alongside his coach during Tuesday's media conference and the Germany international is relishing another opportunity to compete in European football's premier club competition.
"The Champions League is always something special, even if we've been here before," he said. "For a long time it didn't look like we'd qualify automatically for the group stage, so we're very happy to be here. We're hoping tomorrow will be a special evening.
"We've got some difficult games coming up. It's just as important to get off to a good start in the Champions League as it is in the Bundesliga.
"We did well to come from behind to win on Saturday and we want to carry that momentum into this game."