Tottenham have given Reguilon permission to travel to Manchester and undergo a medical with the Old Trafford club.
United have been in the market for a left back since Luke Shaw suffered a muscle injury that is likely to keep the England defender out until November and with his understudy, Tyrell Malacia, also out for the foreseeable future with a knee problem.
Talks had taken place with Chelsea over loaning Cucurella but the costs of doing that deal and the complications around the Spain left back’s appearance in the Carabao Cup for the west London club on Wednesday night led United to switch their sights to Reguilon.
Erik ten Hag, the United manager, also wants to sign the Morocco midfielder Sofyan Amrabat on loan from Fiorentina and the costs involved in trying to do that meant there was less money to commit on a left back given the tight financial limits within which the club are operating.
Additionally, it is thought United wanted a break clause in any loan agreement for Cucurella but the option of sending the player back to Chelsea in January was effectively forfeited by his appearance in the 2-1 League Cup win over Wimbledon on Wednesday since players cannot feature for three clubs in a single season.
Reguilon, 26, who spent last season on loan at Atletico Madrid, is now due to have a medical and finalise a move before Friday’s deadline.
United had originally looked to sign Reguilon three years ago only for the player to instead join Spurs from Real Madrid and leave the Manchester club to instead bring in Alex Telles from Porto.