Marco Fabian is set for a longer spell on the sidelines with an inflammation in the lumbar vertebra region.
Fabian, 27, was one of the key players for Eintracht Frankfurt during their successful first half of the season. However, the Mexico international already was forced to sit out Eintracht's 3-0 loss at Leipzig on Saturday, and is now set to miss the trip to Schalke next Friday as Die Adler hope to bounce back.
"He has an inflammation in the lumbar vertebra region, and it only heals slowly," Frankfurt coach Niko Kovac told reporters on Sunday, adding that it was difficult to say where to locate the inflammation exactly. "He will need a bit of time."
Kovac said that he can't give a return date for Fabian, who is receiving treatment in Berlin.
When Frankfurt make the trip to Schalke on Friday, they will also be without attacking midfielder Ante Rebic, who saw his fifth yellow card at Leipzig, as well as goalkeeper Lukas Hradecky, 27.
Hradecky on Saturday set a record when he saw the fastest red card ever for a keeper in Bundesliga history, and the second fastest overall.
The Finland international had hoped to intercept a long Leipzig pass outside of his box, but slipped and was only able to stop the attack with his hands.
"I am sorry, and I have already issued an apology to everyone, but it was a reflex, and I would do it again," he told reporters. "You don't want to concede a goal as a keeper."
Following the defeat at Leipzig, Frankfurt have dropped to sixth in the Bundesliga standings.