Argentina left-back Marcos Rojo has handed in a transfer request to Sporting Lisbon and told the Portuguese club he wants to leave for Manchester United, Sky sources understand.
Southampton were previously rumoured to be leading the Premier League chase for the 24-year-old before he was linked heavily to United over the weekend.
Saints boss Ronald Koeman said: “We are interested in Rojo but the transfer is a question for the chairman and (executive director) Les Reed.”
Rafael Benitez’s Napoli are interested in taking Rojo to Serie A but new United manager Louis van Gaal is thought to want cover and competition for England left-back Luke Shaw, 19, at Old Trafford.
Rojo did not train with Sporting on Tuesday but United have yet to comment on reports in Portugal which suggest a £16million offer has been lodged for the World Cup runner-up.