Bayern Munich chairman Karl-Heinz Rummenigge has urged Mats Hummels to give his all when Borussia Dortmund take on the Bavarians in the DFB-Pokal final on May 21.
Hummels will leave Dortmund for Bundesliga champions Bayern at the end of the season and will be taking on his new team in his last game for Thomas Tuchel's men.
Rummenigge believes it will be a difficult game for the Germany international centre-back, but has told him not to think about his future employers and do everything within his powers to help Dortmund to cup glory.
"It will an interesting game for Mats, there is no doubt about that," Rummenigge told Bayerischen Rundfunk.
"And it will definitely not be an easy game from a psychological point of view.
"But I can only advise him to give his all for the club he plays for until June 30. That is his job and his only obligation.
"He has to give his all for Borussia Dortmund, it's part of fair play in football."