Aug 28 (Reuters) - Manchester United ( MANU ) have agreed to sell Argentine winger Alejandro Garnacho to Chelsea for 40 million pounds ($54 million), a source close to United said on Thursday.

The 21-year-old's sale value would be the fourth largest for a United player after Cristiano Ronaldo, Romelu Lukaku and Angel di Maria.

Garnacho, who played 93 Premier League matches for United, was among five players seeking to exit the club this summer, along with Marcus Rashford, Antony, Tyrell Malacia and Jadon Sancho. Rashford joined Barcelona on loan last month.

Manager Ruben Amorim has left Garnacho out of his squad this season, as United failed to win their first two Premier League games before being knocked out of the League Cup on penalties by fourth-tier Grimsby Town.

Chelsea host Fulham in the Premier League on Friday. ($1 = 0.7402 pounds)