The Spain international is drawing plenty of interest this summer with both Fiorentina and AC Milan trying to take him to Italy.
Portuguese giants Porto have also made an enquiry and Barcelona are ready to let the 24-year-old leave.
Southampton have been tracking Tello too and now, according to O Jogo, they have firmed up their interest with a £10million bid.
New Saints boss Claude Puel is a big fan of the Spaniard and believes he would fit in perfectly to his new team.
Tello is yet to give an indication as to where he wants to play next season, but Southampton are reportedly able to offer the highest wages.