United States international Aron Johannsson suffered a ligament injury in training with Werder Breman and is set to miss Friday's game against Hannover.
"It's a streak of bad luck," coach Florian Kohfeldt told reporters on Wednesday.
Having struggled with injuries ever since his transfer to Bremen from AZ Alkmaar in 2015, Johannsson, 27, moved closer to Werder's starting formation in recent weeks, especially as he took on a new role on the wing.
Although he has started only two matches under new Bremen coach Florian Kohfeldt, he became a regular squad member again, and played in a 13 competitive games this term.
But Bremen will have to do without the U.S. attacker when they travel to Hannover on Friday after appearing during the closing stages of last week's 2-1 win over Eintracht Frankfurt.
"He's a bit down because he realised that he had a good 20 minutes versus Frankfurt. He wanted to keep it up," Kohfeldt said about Johannsson, who picked up the injury in training earlier this week.
"It's a ligament injury in his ankle. Nothing dramatic. He won't miss several weeks."
While fighting his way back under Kohfeldt, Johannsson has been set back by minor problems in recent weeks, but the Bremen boss said he will continue to trust the attacker.
"I just hope it's a succession of stupid incidents right now," the coach said. "I'd call it a streak of bad luck.
"I hope that he knows I have not lost my trust in him. He should get healthy, and then I know what he's capable of."