Sunderland manager has told Wahbi Khazri and Lamine Kone that they will have to 'do the right things' if they hope to earn a move away from the Stadium of Light.
The two players have been tipped to leave Sunderland as Grayson looks to build a squad that can compete for promotion back to the Premier League, while at the same time trying to save money.
Grayson has praised the duo's attitude, but told the Daily Mail that they must remain professional even though they want to leave.
Grayson said: "If anybody who has wanted to leave the club wasn't doing the work the other lads were doing, then I would come down on them like a ton of bricks and would make sure that they did the stuff because it's part of the discipline you have to have as a manager.
Dutch winger Jeremain Lens has already left the club on a season long loan deal to Turkish side Besiktas, who have the option to buy him at the end of the season, and Khazri and Kone are expected to follow Lens out of the club, providing they behave in a way that Grayson finds appropriate.
"And they have to be respectful that if they are wanting to leave the club, they have to do the right things because ultimately if the club wanted, we could hold people to their contracts."