Chelsea will allow midfielder Nemanja Matic to leave the club if Manchester United offer Matteo Darmian in return.
The defender is believed to high up on Antonio Conte's list of transfer targets and the two have held talks during Euro 2016.
New manager Jose Mourinho would be ready to allow the transfer to happen but only if he can get the Serbia international in exchange.
Matic was one of the most important players in Jose Mourinho's squad at Chelsea and he would be essential for the Portuguese's strategy at Old Trafford.
He was full of praise for his former manager when Mourinho was sacked by Chelsea.
"I've worked with Mourinho two beautiful years, so that means for me he is always linked the good memories," he told Mondo in December.
"I have read several times I think that I had a bad relationship with him, but it is likely to have been written by some idiots.
"I commented with Mourinho about these allegations, we just laughed."