Berlin - Borussia Dortmund boss Hans-Joachim Watzke says he expects Germany defender Mats Hummels will join Bayern Munich next season.
Watzke is battling to keep Hummels at Borussia and the club captain is one of three stars - alongside Ilkay Gundogan and Henrikh Mkhitaryan - who are all out of contract in June 2017.
Gundogan is almost certain to join Manchester City next season while Hummels has been linked with a move to Manchester United.
His agent met City's director of sport Txiki Begiristain in Amsterdam last month, while reports in the UK media claim a five-year contract has already been signed.
Hummels has admitted he is weighing up an offer, most likely from Bayern, while Mkhitaryan has been linked to Chelsea, although he is the one most likely to stay.
Watzke says he expects to lose some - but not all three - of his stars.
"I don't believe that we will have all contracts extended and that all three will play here next year," Watzke told Sky Sports.
"But it is completely out of the question that all three won't play for Borussia Dortmund next season."
Hummels joined Dortmund from Bayern in 2008 after failing to break into the Bavarians' first team.
Having already lost Robert Lewandowski to Bayern Munich on a free transfer in 2014, after Mario Goetze had left for the Bavarians in 2013, Dortmund are eager to avoid seeing Hummels follow suit, but Watzke is realistic.
"I believe that if he (Hummels) goes, it will be in the direction of Munich," said Watzke.
"He still has unfinished business with the club (Bayern Munich). His father, his mother and his brother all live in Munich.
"His girlfriend comes from Munich, he's from Munich too - so a whole lot of components have already come together."
Watzke says he can understand Hummels' deliberations.
"We have to accept when someone like Mats, who has already played for Borussia Dortmund for eight years, is 27 and would come to think: "Am I going to play for Borussia Dortmund for my entire career, or will I do something else?" said Watzke.
However, the Borussia boss told Munich-based newspaper Sueddeutsche Zeitung he would "fight for Mat, like I have never before fought for a player."
Watzke said Bayern - or any other club - would have to "dig really deep in their pockets" to sign Hummels, who has a market value of 32 million euros ($36.1million).
One Bayern star Watzke would like to see playing in the Black and Yellow shirt again is Germany's World Cup winner Goetze, who left in 2013 for 37 million euros, but has failed to make an impact in Munich.
"He came up through the youth teams with and he highly regarded - also by me personally," said Watzke.
"If he came on the market and we received a signal that he was interested to come back to us, we'd discuss it."