Arjen Robben described Jerome Boateng as one of the world's best centre-backs and said he trusted Bayern Munich's leadership to make the right decision over the defender's future.
Boateng has been the subject of reports suggesting he could join Manchester United, while Paris Saint-Germain head coach Thomas Tuchel is also thought to be keen on signing the 29-year-old.
Robben, who has played alongside Boateng in six title-winning Bayern teams, indicated that he would be disappointed to see the World Cup winner leave the club.
"For me Jerome is one of the best central defenders in the world," the Dutch winger said.
"We've had success with him a lot in the past and I know him very well.
"Jerome is simply very important for this team. But we have enough competence in the leadership for the decision."
Should he move, Boateng would become the second big-name player to depart Bayern this off-season following Arturo Vidal's surprise switch to Barcelona.
Robben is adamant the club, winners of just one major trophy last term, should not sanction any further sales.
"I believe that besides any potential new signings it's very important that we don't lose any players - aside from Arturo," he said.
"That is the most important thing because we do have a lot of quality in our team. This has to stay together and then we can be successful. We have talked about our goals already.
"We want to win at least one title more than last season."
