On 11 June 2021, Mbacke was loaned by Los Angeles FC to their USL Championship affiliate Las Vegas Lights.[3] He made his professional debut for the club later that night against San Antonio FC, starting and playing 79 minutes in the 1–1 draw.[4] On September 3, 2021, Mbacke scored a brace in a 4–0 win over Sporting Kansas City.
On 25 August 2022, Mbacke was loaned to Villarreal in Spain until June 2023, where he had previously trained with their youth teams.[5][6] The following day, the loan deal was confirmed, with the player being assigned to the reserves in Segunda División.[7]