Ali Rıza Sergen Yalçın, known as Sergen Yalçın, is a Turkish football commentator, coach and former international midfielder who's the head coach of Süper Lig club Antalyaspor. Yalçın is one of nine players to play for each of the Big Three clubs of Istanbul, and one of only two players who have played for these three clubs as well as Trabzonspor along with Burak Yılmaz. Wikipedia