The club has listed Garnacho for transfer after he had a disagreement with manager Ruben Amorim.
Several teams are interested in signing Garnacho, including Napoli, Chelsea, Aston Villa, Bayer Leverkusen, and his former club Atletico Madrid.
If he joins Bayer Leverkusen, Garnacho will have the chance to work with former Manchester United manager Erik ten Hag, who was in charge when Garnacho played his best football at the club.
Earlier this year, Napoli made a £40m offer for Garnacho, but Manchester United rejected it.