Fatih Terim says Galatasaray's morale was damaged by Schalke's equaliser as the teams drew 1-1 in the Champions League round of 16.
Burak Yilmuz opened the scoring for Galatasaray in the 12th minute at the Turk Telekom Arena and the home side had chances to go 2-0 up in an open and entertaining first half.
Jermaine Jones then equalised in the 45th minute for Schalke to ensure the tie remains in the balance ahead of the second leg.
"We created two great oppurtunities to make it 2-0, then the equaliser damaged our morale just before half time," Galatasaray coach Terim told reporters after the game.
"We went in front with a great goal, but after that made too many sloppy mistakes. We were not at our best and we know there will be no excuses in Germany."
Yilmaz's goal was his seventh of Gala's Champions League campaign and somewhat overshadowed Didier Drogba's return to the competition.
"I'm ecstatic with Burak's form, he keeps working and tries to improve," Terim said.
Terim will hope Yilmaz's scoring run continues when the two sides meet for the return fixture at the Veltins Arena on March 12.