Sevilla midfielder Samir Nasri will miss Wednesday's Champions League home game against Dinamo Zagreb with a muscular injury.
Nasri got hurt during Saturday's 1-1 draw at Sporting Gijon and underwent tests which revealed damage in his left thigh.
A statement from Sevilla said: "Nasri suffers muscular damage in his left femur biceps, an MRI revealed.
"The player's length of absence will be determined once he undergoes further tests."
The 29-year-old is also doubtful for Sunday's home game against Barcelona in La Liga.
Nasri has had a starring role since joining the Andalusian club since arriving on a season-long loan from Manchester City.
The Frenchman has started in nine games in all competitions and scored three goals.
He had the only goal in last month's 1-0 triumph at Dinamo Zagreb in the Champions League which kept Sevilla unbeaten and level on seven points with Juventus at the top of Group H.
One player who will miss this weekend's big encounter against Barca is Argentina defender Gabriel Mercado, who was shown his fifth yellow card of the season and will serve a one-match ban on Sunday.
Under new manager Jorge Sampaoli, the former coach of Chile's national team who is at the helm of a club for the first time in Europe, Sevilla have lost just once, a 3-1 defeat at Athletic Bilbao on Sept. 24.
The Andalusian outfit have won all six of their games at its Sanchez Pizjuan stadium and are fourth in La Liga after 10 games.
Sevilla have failed to progress from the group phase of the Champions League in recent years yet they have been one of the continent's most successful teams, winning the Europa League the last three seasons.
A win on Wednesday coupled with a Lyon defeat against Juventus in the other group game would see Sevilla through to the round of 16 of Europe's elite club competition.