#4 Manchester City - Kyle Walker

Kyle Walker completed a record move from Tottenham Hotspur to Manchester City at the start of last season. He was successful in his first season at The Etihad as the club became the Premier League champions last year. Since then, the English full-back has become an integral part of Pep Guardiola's system at Manchester City.
Manchester United's Ashley Young and Antonio Valencia are in the final stages of their career at the club and the veterans could be looking for a move elsewhere. Diago Dalot and Luke Shaw are still young and hence, United need to prioritize a full-back in the upcoming transfer windows.
Kyle Walker is experienced in the Premier League and can play as a centre-back too. He is a home-grown player is involved in goals very often.
Such attributes make him as Manchester United's top target from their neighboring team.