Atletico Madrid star Koke said Antoine Griezmann must be committed if he remains at the club amid growing links with Barcelona.
LaLiga leaders Barca are reportedly eager to sign Griezmann, who was tipped to join Premier League giants Manchester United in the off-season before opting to remain in Madrid.
Griezmann – away on international duty with France – wants his future resolved before the World Cup in June.
Asked about his in-demand Atletico team-mate, Spain international midfielder Koke told Cadena Cope: "If you want to be here, you will play here, but if you are here you have to be committed.
"If he leaves, it will be difficult to replace him, but we have always managed with what we have had. Others have left and the team have always gone forward."
Meanwhile, Koke reiterated his desire to see out his future at boyhood club Atletico.
The 25-year-old signed a seven-year contract extension at Atletico last May, keeping him at the club until June 2024.
"I have the illusion of finishing my career at Atleti," Koke said. "I have always dreamed it. I am a fan more and I want to play my whole life here.
"I want to continue playing matches with Atleti."