Rashford, a product of Manchester United's own academy, made 426 appearances and scored 138 goals for the club before spending the 2025-26 campaign away from Old Trafford on loan with the Spanish side.
There are strong indications that the 27-year-old England international will not be part of Michael Carrick's plans heading into next season.
According to Sky Sports, if Rashford is sold this summer, United will move to bring in a replacement for the left-wing position.
The Red Devils have identified West Ham United winger Crysencio Summerville as their leading target for that role.
The Dutch international joined West Ham from Leeds United for a fee in excess of £25million in August 2024, signing a five-year contract with the east London club.
Summerville is expected to leave the London Stadium this summer following West Ham's relegation from the Premier League.
The 24-year-old, who plays as an offensive winger, has previously also been linked with clubs including Arsenal and Tottenham as suitors for his signature.
Morgan Rogers, the England international forward, is another player high on Manchester United's wanted list, though Aston Villa are said to be demanding a substantial fee to allow him to leave the club this summer.
Rogers joined Villa from Middlesbrough in 2024 and signed a new contract with the Midlands club running until 2031.
The Red Devils are also considering Senegal international Iliman Ndiaye of Everton and Belgium winger Matias Fernandez-Pardo of Lille as further options for the left-wing role, according to the report.
Ndiaye joined Everton from Marseille in July 2024, while Fernandez-Pardo has been at Lille since returning to the French club in August 2024.
Summerville scored five goals and provided two assists in 31 Premier League appearances for West Ham last season.
His contract with the Hammers runs until the summer of 2029.