He is commonly referred to as "Kalli". Due to his direct and honest interaction with the Turkish media, Turkish newspapers often write about the "Kalli aphorisms."
In June 2007, he returned to Galatasaray by signing a two-year contract and replacing outgoing coach Erik Gerets. He is quite respected and has been elevated to the level of almost a "living legend" by Galatasaray supporters. He is known for his rigid "discipline" on and off the training pitch and doesn't differentiate between "star" and "team" players.
On 5 April 2008, Feldkamp resigned from this position.
He also won the German Bundesliga and the Turkish league once, DFB-Pokal three times as a coach.
As of 05/04/2008, Feldkamp has resigned from Galatasaray due to huge amount of disagreements between himself and the board. Galatasaray President Adnan Polat has previously stated that, Feldkamp would not be Galatasaray coach for the season 2008–2009 but will be responsible for reserve team and as an advisor to the new coach.
It has been rumoured that his previous occasions with Lincoln and Hakan Sukur just before the derby game against Besiktas JK, and recent modifications in the squad led to the resignation.
On 26 November 2008, Feldkamp officially returned to Galatasaray as the team consultant in order to assist the team manager Michael Skibbe.