The Brazil international was forced off an hour into PSG's 2-0 French Cup win over Strasbourg in clear pain, and looked to be in tears as he left the field at Parc des Princes.
Neymar limped heavily as he walked to the dressing room, consoled by a PSG staff member, and looked upset as he wiped his face with his right arm.
It was unclear how Neymar sustained his latest injury but he had been on the receiving end of a heavy tackle from midfielder Anthony Goncalves earlier in the match.
TV images then later showed Neymar rolling off his sock and pointing to the side of his right foot, which he also fractured nearly exactly one year ago while playing in the French league against Marseille.
"Neymar is worried, because it's the same foot, the right foot, in the same area," Tuchel said. "There's no news for the moment, he's gone to hospital. I need to wait for the doctor to give me news about Ney."
PSG confirmed on Thursday morning that he has indeed injured the same fifth metatarsal in his right foot as he did last year which saw him miss the remainder of the season. Although he recovered in time for the World Cup last summer, he was not at his best in Russia.
Tuchel believes his player was not protected enough on the pitch.
"The referee didn't whistle on one occasion, then two, then three and after that he ended up twisting his foot," Tuchel said.
For his part Goncalves expressed no sympathy and even suggested the injury is a direct result of how he plays.
"It's his style. But if you play like that don't complain if you take some knocks after," he said afterwards. "He's a great player, and I respect the player he is, but we're not here so he has fun at our expense. We're not here to make him look good."
Goncalves suggested Neymar, who has a tendency to showboat and even toy with opposing players with his skillful trickery, lacks humility.
"If he wants to have fun, we'll respond with the weapons we have. We have a jersey to defend. We're not here for a laugh," Goncalves said. "He can amuse himself, that's his style and I think people come to watch that.
"But he shouldn't come and moan about it afterward (and) he likes to do that. It's part of his arsenal and we respond in our way."
PSG travel to Old Trafford on February 12 before the return leg three weeks later in the French capital.
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