Manchester United are stepping up their search for a new full-back, a source has told ESPN, with Tyrell Malacia set for a further spell on the sidelines.

Malacia hasn't played for more than a year because of a knee injury.

There had been hope that he would be able to return to training this summer, but the 24-year-old, who last played for United in May 2023, was omitted from the squad which travelled to Los Angeles on Wednesday as he continues his recovery at Carrington.

A statement on the club website read: "Tyrell Malacia is absent from the squad as he continues his rehabilitation from injury under the guidance of medical staff at Carrington."

A shortage of left-backs last season, compounded by Luke Shaw's injury problems, persuaded United to sign Sergio Reguilón in a short-term deal last summer.

Erik ten Hag was also forced to use emergency options Victor Lindelöf and Sofyan Amrabat.

Shaw will also miss the U.S. tour after featuring for England at Euro 2024 leaving United with just 17-year-old Harry Amass and 19-year-old Sam Murray as the only recognised left-backs for games against Arsenal, Real Betis and Liverpool.

A source has told ESPN that the club are looking at left-back options during the summer window to avoid a repeat of the problems which dogged last season.

United are also looking at right-backs if they can find a club to meet their 20m valuation of Aaron Wan-Bissaka, who has entered the final year of his contract at Old Trafford.

Diogo Dalot, Bruno Fernandes, Alejandro Garnacho, Kobbie Mainoo, Lisandro Martínez, Facundo Pellistri and Altay Bayindir will also miss the U.S tour after being given extended breaks following the European Championship and Copa América.

Meanwhile, United have announced that Rasmus Højlund has taken the No. 9 shirt.

The number, previously worn by Zlatan Ibrahimovic and Romelu Lukaku, was vacated by Anthony Martial after the Frenchman left the club at the end of last season.