Real Madrid coach Santiago Solari has rejected Isco's claim that he is not getting the same opportunities as his teammates.
After indicating on Thursday that he felt he was being unfairly treated, Isco featured in Friday's training session but suffered a back complaint and is unlikely to feature at Atletico Madrid on Saturday.
Asked at his prematch news conference about Isco's claims, Solari said: "The job of a professional footballer is to train at 100 percent to be ready for the team.
"All our players are training very well in every session, so that the team can be on the front foot in games.
"Being a footballer is about working hard and putting your talent to the service of the team. All the players are thinking of the team, and focused on the next game."
Solari confirmed that Isco "left the training session with a problem in his back" and said the injury would be assessed later on Friday.
Isco, a regular under former coach Julen Lopetegui, has barely featured since Solari took over in October, starting three games in four months.
With Madrid's results improving, former midfielder player Ruben de la Red backed Solari.
"Real Madrid does not wait for anyone. Everyone in the squad is a very good player. Whoever is not up to it gets passed by his teammates. Madrid have improved a lot since Solari took over," he said.
Isco responded to those comments by writing on Twitter that he felt the competition for places was not entirely fair.
"I agree completely with De La Red but when you do not enjoy the same opportunities as your teammates then things are different... but even still I keep working and battling a lot hoping for them. Hala Madrid!!" he wrote.
De La Red, who also worked as a youth coach at the Bernabeu and is currently in charge of Getafe B in the third tier, responded by saying: "My words were not to criticise Isco, but for people to understand the demands of playing for Real Madrid, with the players that surround you.
"If we talk about Isco, we have a player who has given the Bernabeu some magic moments."
Isco has shown recent signs of frustration, snubbing Madrid match delegate Chendo after getting only four minutes as a substitute in last weekend's win over Alaves.
Atletico, meanwhile, have been lifted by the return of captain Diego Godin from injury, although Spain internationals Koke and Diego Costa look set to miss out.
Midfielder Saul Niguez is also expected to return from injury, while Alvaro Morata, who had a disappointing debut against Real Betis, is set for his home bow against the club where he began his career.