The 22-year-old, who can play at left-back as well as further up the flank, is close to joining the Black Cats, potentially as a temporary replacement for Kieran RichardsonSunderland are nearing the loan signing of Tottenham winger Danny Rose.
The 22-year-old, who made four appearances for the Team GB Olympic team this summer and can also play at left-back, is behind the likes of Gareth Bale and Benoit Assou-Ekotto in the pecking order for places at White Hart Lane.
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The development comes after the Black Cats boss revealed on Monday that Kieran Richardson, who is similarly positionally versatile to Rose, has asked to leave the club.
The Tottenham youngster has made 29 first-team appearances for his side, scoring one goal, as well as several loan spells in lower divisions but looks likely to get more game time under O'Neill.
Sunderland, who drew their opening fixture of the Premier League season 0-0 against Arsenal, are also close to signing Manchester City misfit Adam Johnson for £11 million.