Southampton fear losing Jose Fonte in January.
The Sun says Fonte has not signed a new deal despite being in talks since August – his current contract running out in 2018.
Fellow countryman Jose Mourinho wanted to make Euro 2016 winner Fonte a summer signing, keen to add his experience to his squad – but new boss Claude Puel did not want to do business so late in the window.
And after United's poor start to the season, coupled with injuries to the likes of Chris Smalling and Eric Bailly, the Special One is poised to return for Fonte.