Barcelona have confirmed that Sergi Roberto was taken off during Saturday's 3-0 win over Eibar with a knee problem.
Ernesto Valverde appeared to have made the surprise move to removed Roberto at half-time, with Nelson Semedo coming on in the right-back position.
Roberto had not appeared to be injured during his 45 minutes on the pitch but Barça later confirmed he had an issue with his knee which is why he was taken off.
The Catalan club added that he will undergo further tests this weekend to determine the severity of the problem.
Barça eased to a 3-0 win at Ipurua, with Antoine Griezmann, Lionel Messi and Luis Suarez all on target in the success.