Borussia Dortmund will struggle to replace "leader" and "role model" Mats Hummels once he rejoins Bayern Munich in the summer, according to Ottmar Hitzfeld.
Hummels, who joined Dortmund from the Bavarians in 2009 after a successful loan spell, will head back to Allianz Arena at the end of the 2015-16 season for an undisclosed fee.
The 27-year-old has established himself as one of Dortmund's most integral players over the past seven years, which included back-to-back Bundesliga titles in 2010-11 and 2011-12.
However, with the BVB captain and World Cup winner now on his way back to Bayern, Hitzfeld admits Dortmund are going to find it tough to find a replacement.
"Hummels leaves a big gap in the team of Borussia Dortmund. You can't replace Hummels equivalently," Hitzfeld, who won the Champions League as Dortmund coach in 1997, told Omnisport.
"Sure, you can buy a very good defender, who has a lot of class. But you can't make a new player the captain immediately.
"You can't find a comparable player, as he is also the leader within the team. He's a leader, a role model, he knows the team, he knows the surroundings, and he can lead other players.
"He will leave a big gap in the team of Dortmund."
Hummels joins Robert Lewandowski and Mario Gotze to make the switch from Dortmund to Bayern in recent years, much to the disappointment of the Signal Iduna Park faithful.
However, Hummels still has one game left to play in Dortmund colours - against Bayern in Saturday's DFB-Pokal final.
And Hitzfeld says the defender has the perfect chance to say goodbye to the Dortmund fans as a winner of the competition for a second time.
"You have to see that the fans of Dortmund love their club and that they don't understand it if you go to another club, especially if it's the rival Bayern Munich," the 67-year-old added.
"It hurts them to lose the captain. Hummels is the soul of the team and one of the best players. So the disappointment was normal.
"That you get booed belongs to professional sports. It's not nice and it's difficult for the player who had great performances for the club for eight and a half years. But as a professional player you have to deal with that.
"I think the fans of Dortmund have let off steam and will support even Hummels in the final, because they want to win the title. Hummels could have a great goodbye by winning the title."
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- Goal