The Royal Blues go into the second leg with the advantage after a 1-1 draw in Turkey, but on the back of a physically and emotionally draining 2-1 win over Dortmund in which they also lost striker Klaas Jan Huntelaar to a knee injury.
The Holland frontman is out of the return leg but coach Jens Keller claimed his side would be ready for the match.
He said at the press conference: "The lads are physically very fit. I think they have shown that impressively in recent weeks.
"And so if anyone should feel tired, this feeling will evaporate at the latest when they walk into the stadium and hear the Champions League anthem.
"We will of course take the positive feeling of the derby win into this game. The euphoria and the way we played our football against Borussia Dortmund and were supported by the fans was very special and can definitely help us against Galatasaray."
Midfielder Julian Draxler will be expected to pose some of the hosts' attacking threat in the absence of Huntelaar and said the team were raring to go.
"We want to take in the momentum and confidence from the victory in the derby and reach the quarter-finals," the 19-year-old said.
Keller revealed Finland international Teemu Pukki was "an option" to come in for Huntelaar to lead the line.
Turkish Super Lig leaders Gala have had one more day to prepare than their hosts, but suffered an embarrassing 1-0 home defeat to Genclerbirligi in their last outing last Friday.
But Keller insisted he was not reading anything into that performance.
"Galatasaray's weak last league game does not interest us, the Champions League is a different competition," he said.
It was of concern, though, to Gala boss Fatih Terim, who branded it "unworthy of our club" and demanded an immediate improvement.
"In the league you can make up for lost points, but in continental competition weak performances are punished," he was quoted as saying by kicker.de.
"On Tuesday we have to improve our level significantly."
Gala can call on Champions League winners Didier Drogba and Wesley Sneijder, but Draxler warned Schalke could not just focus on stopping those two.
"They are very strong as a team too," he said.