The Brazil international has been nursing a rib injury and last played for PSG in their 5-0 win over Montpellier on February 1.
However, Neymar was involved in training on the eve of the match and is now expected to start the clash at the Westfalenstadion.
"He is here, he will train and if all goes well he will play," Tuchel told reporters. "Because for us it changes almost everything when he plays and I hope he will play.
"He changes everything because if he plays we have his quality and confidence and ability to do decisive.
"If he does not play we have no other player with that quality to replace him."
PSG have been eliminated from the last-16 stage of the competition for three seasons running. body check tags ::