After attending PSG's foundation gala on Wednesday, Neymar hopped on a plane and went to Brazil, missing PSG's training session on Thursday.
Despite not being able to play the final match of the season for PSG, he skipped training without Tuchel's permission.
"Was he authorised by PSG? No, not by me. It's not to do with sport, it's not up to me to decide whether or not to authorise his absence," said the German coach in the press room, visibly annoyed by the umpteenth issue with his Brazilian striker.
In the midst of speculation about his future after the media explosion with Mbappé, Neymar did not go to the last training session of the season, instead flying to Brazil, where he will begin to prepare for the Copa America.
Tuchel wanted to lower the tension in the press room by saying he wanted Neymar at PSG next season: "This is football! We're not naive, the clubs want to sign a lot of players, but if you ask me, as a coach, I do want him to be here next season. If that doesn't happen, we'll find solutions."