Borussia Dortmund CEOHans-Joachim Watzke has defended Bayern Munich centre-back Mats Hummels after it emerged the 27-year-old visited his former club'schanging room ahead of the two side's match on Saturday night.
Hummels made 227 Bundesliga appearances during his time with Dortmund before making the switch to bitter rivals Bayern Munich. The likes of Mario Gotze and Robert Lewandowski have also switched in recent years, and Hummels was booed by Dortmund fans throughout the match.
The changing room visit was criticised by former Bayern Munich and Germany midfielder Lothar Matthaus, who claimed "before the game, the concentration should be on the game and not the old friendship," according toESPN.
However, Dortmund CEO Watzke praised Hummels' conduct, claiming it showed the Germany international's 'human qualities'.
"I found the action of Mats Hummels, far ahead of the game, the old fellow in the booth to visit, great," Watzke said at Dortmund's annual shareholder meeting, as reported by Welt.
"If I then hear, that is unprofessional behaviour, I must puke. This again shows Mats' human qualities."
Hummels joined Dortmund in 2008, initially on loan before making the move permanent after finding his opportunities at Bayern limited.
He won the Bundesliga twice during his time at theWestfalenstadion, becoming established as a permanent fixture in Germany's squad before making the move to Bayern this year.
Dortmund won the Der Klassiker 1-0 thanks to an early goal from Pierre-Emerick Aubameyang, and took the club up into third place in the Bundesliga. Bayern lost their place at the top of the league thanks to the defeat, withRB Leipzig taking top spot after their victory over Bayer Leverkusen.