The Brazil forward returns from a two-game suspension after his dismissal in a controversial clash with Marseille earlier this month, when five players saw red.
PSG has won both Ligue 1 games in his absence, with fellow forward Kylian Mbappe having made a goal-scoring comeback in the 3-0 win over Nice last week having completed a period of isolation after a positive test for coronavirus.
Tuchel said having the duo available would transform the way his side can play.
"Yes, when Kylian and Neymar play it changes everything for us," he said.
"If both play for us, it's harder [for the opposition] to defend and easier for us to attack.
"We found solutions without both. We started the last Champions League, the group stage, with matches without them.
"It [missing Mbappe and Neymar] is not the best thing. They are there to make the difference. They will start together, that's for sure."
Leandro Paredes, sent off in the same game as Neymar, is also back in the frame along with Abdou Diallo, who got his marching orders in the win over Metz.
But one player still missing is Angel Di Maria, who is serving a four-match ban for spitting at Alvaro Gonzalez in that contentious Classique contest.
While Tuchel accepts Di Maria's sanction was deserved, he vented his frustration at the fact PSG has seemingly suffered significantly greater suspensions than Marseille in the aftermath of that game.
"I can understand the sanction of Di Maria," Tuchel said. "He had a reaction that we don't like.
"[But] we have suspensions that equate to 14 matches, the other team [Marseille] has four matches. There is a big difference in the number of suspensions.
"I do not accept it but I have to and I do not understand. We have the impression that we are the only ones responsible for this situation."