Newcastle boss Eddie Howe admits Allan Saint-Maximin is in talks to leave the club.
The winger was left out of yesterday's preseason friendly win at Rangers.
"He's in early discussions over a potential move away. That's why he wasn't here," Howe said.
"It's doubtful he'll join us on the tour of America. I don't think Maxi necessarily wants to leave, but he may feel it's the right time for him to move.
"It's difficult for me to speak for him, but he hasn't asked to leave. There's been no issue between him and any of us coaches. We all love him.
"If he does leave, we'd lose him with a very heavy heart. He's someone we love working with, he's a difference-maker, we've really had a strong working relationship, and it'll be sad if he leaves.
"Maxi is the player that's generating the interest. FFP is a new dynamic which really came to the fore after my first window here when we knew it would impact us.
"Player trading is a key part of it - you can't hit it, if you don't trade. We're forced to trade a player this window.
"If the deal didn't go through, I'd be delighted. It would obviously impact our ability to bring any more players in, and then we potentially might have to sell another player. That's the way that Financial Fair Play has hit us."