Southampton boss Ronald Koeman has already lined up Feyenoord's Jordy Clasie as a potential replacement for Morgan Schneiderlin but told Manchester United the France international will only leave at the right price.
Koeman has said United's last bid for Schneiderlin, reported to be £20 million, was "not serious" and The Guardian says Southampton are holding out for £27m for the midfielder.
The 25-year-old, who signed a four-year contract in 2013, had been forced to stay at St Mary's last summer after the club allowed Rickie Lambert, Luke Shaw, Calum Chambers, Adam Lallana and Dejan Lovren to leave.
Koeman said Schneiderlin would be allowed to exit this summer but only if a suitable offer came in.
"Every player has his price and we have experience as a club of selling players," Koeman told reporters. "Last season we sold some players, and if there is interest in Morgan then OK, but it has to be at the price the club wants.
"He is one of the key players of our team, an international player, and I don't think is a problem for Manchester United."
He said he was not planning for the coming season with the expectation that Schneiderlin would still be in the squad and added: "I know the situation. I have spoken a lot with Morgan.
"Last season we finally said: 'Stop all this business because we are not selling any more players.' That was difficult for him but he came back after a few days with good motivation and had a great season, but we know the situation now.
There is a lot of interest in the player. With a club like United, we know it's difficult to keep the player, but if they pay then, OK, we can make the transfer."
Koeman said he was looking to raid former club Feyenoord to sign Netherlands midfielder Clasie if Schneiderlin does depart.
The 24-year-old came through the youth ranks at De Kuip, where Koeman was in charge from 2011 to 2014, and is the Eredivisie side's captain.
"Clasie is one of the players on the list what we have to replace Morgan Schneiderlin," he said.
"He's a good player, a young player and a Dutch international who is ready to make a step up and show his qualities at a higher level than we have in the Dutch league.
"He's growing in his leadership qualities too and, if Morgan goes, we'll need a player in that position."
Southampton -- who defied expectations to finish seventh last season -- have already been busy in the transfer market this summer.
Nathaniel Clyne was allowed to join Liverpool, with Portugal international Cedric Soares arriving as a replacement, while Netherlands goalkeeper Maarten Stekelenburg has joined on loan from Fulham as cover for injured goalkeeper Fraser Forster.
Spanish striker Juanmi has also joined from Malaga.
"I think we did some good business, bringing in some new players like Stekelenburg, Cedric as a replacement of Nathaniel Clyne, and Juanmi," Koeman said.