Southampton centre-back Jose Fonte is keen to join Manchester United but he has also received an approach from Arsenal, sources have told ESPN FC.
Jose Mourinho is seeking an experienced defensive leader and club sources told ESPN FC in recent days that United had opened informal talks over 32-year-old Fonte, who could play for Southampton at Old Trafford on Friday night.
However, United need to sell or loan one of their existing central defenders before signing Fonte, with Argentina international Marcos Rojo the player the club are most eager to offload.
United also have Chris Smalling, Eric Bailly, Daley Blind and Phil Jones as centre-back options. Cameron Borthwick-Jackson prefers to play as a central defender, but he was told by Mourinho that he is free to go on loan this season.
The problem, as United found when Louis van Gaal wanted to trim his squad, is that their players earn too much. Moving would invariably mean taking a pay cut unless United make up the shortfall or even fund the majority of their wages.
Portuguese agent Jorge Mendes is working on the Fonte deal with his existing client Mourinho and United's executive vice-chairman Ed Woodward.
Fonte, the Southampton captain and a Euro 2016 winner with Portugal, has also been approached by Arsenal.
The Gunners have lost Per Mertesacker and Gabriel Paulista to long-term injuries. Arsenal, who lost their Premier League opener 4-3 at home to Liverpool, have been holding talks over Valencia defender Shkodran Mustafi, but the Spanish side are under no pressure to sell their best defender and are pushing for £30m for a player who cost only €8m (£6.94m) from Sampdoria in 2014.
Laurent Koscielny is fit again, though he is still working on his match fitness after his post-European Championship break, but Arsenal are still short.
Fonte, who would command a fee of around £10m, would be a cheaper option and one who has been consistent in the Premier League.
He has two years left on his contract at Southampton, whom he joined from Crystal Palace in 2010 when the Saints were in England's third tier, and has been in a key part of the club's rise back to the top flight.
Sources have told ESPN FC that Mourinho considers him reliable, technically good and able to read the game well.
He has also improved with age and made his Portugal debut in 2014, aged 30, when he played against Argentina in a friendly match at Old Trafford, and he has gone on to form an excellent partnership with Real Madrid's Pepe for his country.
Although he spent time with Benfica earlier in his career, Fonte has never played first-team football for an elite club, and sources said that is why the prospect of a move to Manchester United or Arsenal is so attractive to him at this point, and he is particularly enthused at the prospect of working under his compatriot Mourinho.
However, Saints boss Claude Puel said earlier this month that he was confident Fonte would stay at St Mary's and the local Daily Echo newspaper has said the club remain hopeful he could sign a new deal.