Are you sure about this? Maybe it was addressed to Messi who, after his transfer, had the worst season of his career? There are rumors that PSG want to get rid of both Neymar and Messi already, but I would not be sure about Messi since he is part of the promotional campaign for the World Cup held in Qatar. Perhaps after the tournament he will be sold, but not before.
Well i would guess that the message was adressed to the whole team as most players of PSG did not really reach their maximum potential last year. Regarding Messi i think it is no big surprise that he did not reach the performance level that he had in Barcelona because Messi is a player that needs to feel comfortable in order to Show great performances and i don't think he feels that way in Paris. I mean he did not even want to leave Barca in the first place.