Real Madrid head coach Zinedine Zidane is unsure how long Eden Hazard will be sidelined, but said the attacker was "upset" after another injury setback.
Hazard, 29, is enduring a torrid run in Madrid, and is yet to make an appearance this season.
The Belgium international was ready to return from an ankle problem, but suffered a muscle injury that saw him miss Wednesday's 1-0 LaLiga victory over Real Valladolid.
Zidane is unsure how long Hazard, signed for a reported €100million from Chelsea last year, will be unavailable.
"I can't tell you how long it'll be. He picked up a bit of a knock in training before the game," he told a news conference.
"It looked like a muscle spasm but in the end it turned out to be a bit more than that. It's something muscular. It's nothing to do with the injury he's had and these things happen.
"He's been out for a long time. I don't think this one will be long but I can't tell you exactly."
Hazard has struggled to impress since arriving at Madrid, where he scored one goal and provided three assists in 16 LaLiga appearances last season.
Zidane said the former Lille star was disappointed after his latest injury.
"He's upset because he was all right. We talked about it at the press conference before the match, but he's had a setback and these things can happen," he said.
"He's not happy, he knows that it's not a big thing and we have to take it easy with him. It's a question of little time, I'm sure."
After earning seven points from their opening three LaLiga games, Madrid visit Levante on Sunday.