Dedryck Boyata said he is ready to step in for Vincent Kompany if the defender fails to recover from a groin injury in time for Belgium's World Cup opener against Panama on June 18.
Kompany, 32, was injured in a friendly against Portugal on June 2 and did not train along with the rest of the team on Saturday.
"If I have the chance to play, of course I will be very happy," Boyata, who came on as a substitute for Kompany and would be again expected to fill in if the Manchester City defender fails to regain fitness for the tournament, told Sky Sports.
"I know he has been working very hard [to return]."
The injury is the latest in a long line of fitness problems for Kompany, who managed just 17 Premier League appearances for City last season.
However, he told RTBF he believes he will be fit in time.
"I am confident it will be OK," Kompany said. "I feel good and have often fought back.
"The goal to play at the World Cup is in my head and I try to achieve that."
But Belgium midfielder Kevin De Bruyne suggested Kompany may only be available for later games.
"He may not be there for the first games in Russia but the team can play the group stage without him," he told reporters.
After their opener, Belgium face Tunisia on June 23 followed by a potential group decider against England five days later.