Didier Ndong has told Sunderland he wants to quit the club this month - but Chris Coleman says the deal must be right for Sunderland.
Club record signing Ndong is seeking a move during the transfer window just 18 months after his £13.6million switch from Lorient.
Read Sunderland fans' reaction to Didier Ndong's return to training
Premier League side Watford have been heavily linked with a loan move for the Gabon midfielder, but Coleman has warned potential suitors that any deal will have to be a permanent transfer.
He said: "What do we get out of (a player leaving on loan)? If it's a loan deal and he has to play 75% of games for a fee to be involved, he will probably only play 73%.
"They must think we have fallen off the back of a lorry.
"There will be no loan deals.
"We have had a couple of enquiries about Didier but just loan deals and that's not something that's for us unless there's an absolute guarantee at the end of it.
"It's common knowledge Didier wants to leave. He sees his future elsewhere but we have got to do what's right for us."
Ndong has been out injured since before Christmas but returned to training this week, though he won't be available for tomorrow's game against Cardiff City.