Die Knappen were the better team in the first leg of the Champions League last-16 clash, but were held to a draw at the Turk Telekom Arena.
Still, the Bundesliga outfit find themselves ahead as they travel back to Germany courtesy of the away-goal rule.
Keller, aware of the intimidating atmosphere that Cimcom fans can create on their home patch, has said that he is pleased by the performance of his players.
"My side put in a great performance," he told UEFA.com. "We were compact and determined and played as a team. We created a few chances, but unfortunately missed a couple as well.
"It was a very aggressive and determined performance. We worked hard and were compact. We played well and I'm very happy with my team's display.
"They faced the crowd without any fear."
The return leg will take place on March 12.