David Moyes has confirmed Sunderland have rejected an offer for Patrick van Aanholt and also dismissed reported interest in Adnan Januzaj as "pure speculation".
The bid for Van Aanholt is thought to have come from Crystal Palace, now managed by former Sunderland boss Sam Allardyce, but Moyes is not willing to sell.
"Yes (we have rejected a bid). He's a really important player for us and he's got an awful lot going for him," said Moyes at a news conference ahead of Saturday's home game with Stoke City.
"He's still young and yet still has a lot to learn. But he's done very well, he's earned us points by his goals and assists this year.
"We've actually had a bid for quite a lot of our players, because we've got some good players here and maybe people think we could be easy pickings but we're not.
"I want to keep all our good players. I want us to keep them here. I want us to build and I want us to add to our group rather than lose players."
On-loan winger Januzaj is reportedly interesting Lyon but Moyes has heard nothing from his parent club Manchester United or the player himself.
"If there's a sale yes, [United can recall him]," added the Scotsman.
"The reason I'm shocked is because I've heard nothing about it and I'm sure the first people United would contact is us if that was the case.
"They would contact us if we were going to lose a player and I haven't heard anything from Adnan either so I take it as pure speculation."
Sunderland could climb out of the relegation zone with a win on Saturday and Moyes is hoping to make the Stadium of Light a fortress over the second half of the season.
"We need our home form and we're going to need the supporters right behind us," said Moyes.
"January can be a month which defines a season and a couple of wins for us can make it look a lot healthier."
The Black Cats boss confirmed Victor Anichebe and Steven Pienaar would miss the weekend clash through injury, but had positive news regarding goalkeeper Jordan Pickford, who is believed to be 3-4 weeks away from a return to action.