Bayern Munich captain Philipp Lahm says there is no guarantee that Thomas Muller will not follow Bastian Schweinsteiger to Manchester United.
Muller, 25, has been linked with United this summer and on Monday German TV channel Sport 1 claimed that the English club had offered €100 million for the Bayern attacker, while The Guardian has said he is open to a move.
United have identified Barcelona's Pedro and Bayern's Muller as top targets as they look to bring in a new forward, sources told ESPN FC at the weekend.
Speaking at a news conference in Shanghai on Tuesday, Lahm, 31, admitted that it is conceivable that the Germany international could leave for the Premier League.
"In football you can imagine everything," he said. "It's not my decision. In football, it goes so, so quickly.
"It's not always only up to the player. There are clubs who get players, players go.
"In football everything goes very, very quickly. I think you can never give a guarantee that it will work like this or like that.
"As a result, I certainly can't give any guarantee for Thomas Muller or talk about whether I can imagine [him leaving]. You can always imagine anything happening."
But Germany's captain at the 2014 World Cup is not concerned that Bayern could struggle to compete, while also expressing his belief that they will ultimately hold on to Muller.
"We're still a top club that every year, or in the last few years, has made at least the Champions League semifinal," he said.
"We have a top team that's very well-equipped this year as well and that can challenge on all fronts.
"So you don't have to be worried about anything. And I'm definitely not worried about Thomas -- I don't think we're going to let him go."
Meanwhile, Bayern full-back Rafinha is applying for a German passport, leading to speculation that he could try to switch his allegiance at international level.
The Brazilian, 29, moved to Schalke in 2005 before returning to Germany to sign for Bayern in 2011 after spending a year with Genoa in Italy.
Rafinha has played twice for Brazil at senior level but neither was a competitive match. He did, however, help Brazil to win bronze at the 2008 Olympic Games.
Right-back has been a problem position for Germany since Rafinha's club teammate Lahm retired after captaining the side to World Cup success in 2014.
But the player did not confirm if he would investigate whether he is eligible to play for his adopted country.
"It's still too early," Rafinha told Tageszeitung. "Let me get my passport first and then we'll see."