Manchester City captain Ilkay Gundogan admitted on Monday he did not have the stamina to keep up with "party machine" teammate Jack Grealish after his side celebrated claiming the treble.
Speaking upon his return to the German national team ahead of Tuesday's international friendly clash with Columbia in home town Gelsenkirchen, Gundogan said the 27-year-old Englishman's antics did not come as a surprise.
"You've all seen what a party machine Jack is," Gundogan told a press conference in Frankfurt.
"It wasn't surprising to me. He put everyone on his back and just carried us along."
The 32-year-old former Borussia Dortmund player added: "I can't manage two nights in a row. I needed a little break and a rest."
Pep Guardiola's team won a historic treble of the Champions League, Premier League and FA Cup last season -- becoming just the second English side to manage the feat.
Gundogan, who is out of contract in the summer, said "no decision had been made" yet on his future, amid links to a move to Barcelona or even a return to Dortmund.
The midfielder said while talks had taken place with Dortmund "the probability was not very high" of a return, while admitting Barcelona "is a very beautiful city".
Earlier on Monday, Hansi Flick revealed Gundogan was in line to captain Germany for just the fourth time on Tuesday should Bayern Munich midfielder Joshua Kimmich start from the bench.
