The France forward, who scored four goals in the Champions League last season, combined with Neymar for the Brazil superstar to score the only goal in a 1-0 Ligue 1 win.
Neymar is out for Tuesday's trip to Turkey, though, as he serves the final match of a two-game European ban, but Mbappe's return improves PSG's attacking options.
"Mbappe can start the game or finish it but he cannot play the whole 90 minutes," Tuchel told a news conference.
"We have specific goals, yes, but I cannot communicate them to you in a press conference, it stays between us.
"There are always things to work on, the precision in the last touch, finding spaces but also tactical points.
"It is important that he regains all his confidence already, he had many opportunities in the last game, it's a good thing.
"I will not stop pushing him, with help you play with the best possible state of mind."
Although Mbappe is back in contention to start, PSG's record goalscorer Edinson Cavani is still sidelined and Mauro Icardi was an unused substitute in the weekend win at Bordeuax while Eric Maxim Choupo-Moting is another injury doubt.
Tuchel's PSG have typically lined up with a front three but the German suggested he could switch formation in Istanbul.
"I cannot tell you everything before a big match, it's always a challenge for us to find solutions," Tuchel added.
"We managed against Real, we'll see, maybe we'll play with two attackers, maybe with three...
"We will make the decision tonight or tomorrow morning, we will present our plan tomorrow, at the meeting, to the players.
"We must wait for returns from Choupo, Mauro, see how their situation evolves."