Manchester United are keen on signing Kieran Trippier and are monitoring his situation at Atletico Madrid.
The England right-back will enter the final 18 months of his Atletico contract in January.
Trippier, a former Manchester City youth player, moved to Atletico from Tottenham in the summer of 2019, signing a three-year deal.
United's first-choice right-back Aaron Wan-Bissaka currently has competition only from Timothy Fosu-Mensah, with Diogo Dalot having joined AC Milan on loan in the summer.
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Trippier, 30, has made 48 appearances since joining the Spanish club, with 15 of those coming this season.
Diego Simeone's team have made a formidable start to the 2020/21 La Liga season.
Atletico are the Spanish top-flight's current frontrunners, having won their last seven league games, and they hold a one-point lead over second-placed Real Sociedad, with two games in hand.
Meanwhile, United playmaker Jesse Lingard could be set to leave Old Trafford on loan in the upcoming transfer window, with his representatives currently exploring the midfielder's options. Real Sociedad are one of the clubs they have held initial talks with.
Doubt has again been cast over Paul Pogba's future at United after his agent Mino Raiola claimed the France international is "unhappy" at the club and needs to secure a move away in the 2021 summer transfer window.