Barcelona's Dani Olmo has been ruled out of Sunday's Clásico against Real Madrid with an adductor injury that will sideline him for a month.
Olmo, 28, picked up the knock in the first half of Tuesday's 4-2 Champions League defeat to Paris Saint-Germain.
He returned to Barcelona on Wednesday, where tests subsequently confirmed "an injury to his left adductor muscle," his club said in a statement.
In addition to the Madrid match, Olmo will also miss league games against Alavés and Atlético Madrid, as well as the Champions League fixture with Aston Villa, but he could return after the November international break.
The Spain midfielder has struggled with muscle issues throughout his career, but he had been playing injury-free for club and country since January.
Olmo was replaced against PSG by Fermín López, who is now also likely to start at the tip of Barça's midfield ahead of Rodri and Pedri against Madrid.
Barça will also be without Eric García, Andreas Christensen and Roony Bardghji for this weekend's Clásico.
Jules Koundé is a doubt as well with the ankle problem which forced him to miss the match against PSG.
After suffering their first defeat of the season in Paris, Barça will look to get back to winning ways when Madrid visit Spotify Camp Nou.
Hansi Flick's side have the chance to continue their perfect start in LaLiga by making it 10 victories in a row, which would see them build a nine point lead over José Mourinho's side at this early stage of the season.