The pair were a surprise addition in Bayern's 4-0 demolition of title rivals Borussia Dortmund on Saturday and despite only just returning from injury should be ready for Wednesday.
"We did not train on Sunday and their first actions were positive (on Monday in training)," Tuchel told a press conference on Tuesday. "I assume if nothing happens until tomorrow they will both be able to play tomorrow."
However, with a busy schedule ahead and another Bundesliga game on Saturday against promoted Heidenheim, the Bayern coach said he would not overwork France international Upamecano following his recovery from a hamstring injury in October.
Goretzka is playing again following surgery for a broken bone in his hand.
Bayern are without fellow central defender Matthijs de Ligt, with the Dutchman having been sidelined for several weeks with a knee ligament injury.
"If Upa (Upamecano) plays tomorrow then it will influence the situation as it would not be responsible for us to give him double matches per week from the start," Tuchel said.
He will also have Joshua Kimmich back for their Champions League match, with the holding midfielder serving a two-match suspension in the Bundesliga for a red card and having missed their win at Dortmund.
"In my plan, he will play tomorrow," said Tuchel. "We know he cannot play on Saturday but tomorrow Josh will play and show his qualities.
"Apart from De Ligt we plan with everyone apart from Raphael Guerreiro, with Wednesday's match coming a little too early," he added as the Portugal international recovers from injury.
Bayern, who are unbeaten in a record 37 Champions League group matches and have won each of their last 16 group games, also a competition best, could qualify for the knockout stage with a win on Wednesday.
The Bavarians have nine points from three matches, five ahead of Galatasaray and six in front of third-placed Manchester United. FC Copenhagen are bottom with one point.
"Our desire is to qualify as early as possible," Tuchel said. "It will give us huge self-confidence. We know tomorrow is a big, tough step in that direction."
