Adnan Januzaj left Old Trafford for the San Sebastian side in 2017 and has made more appearances for the Basque outfit than any of his other clubs.
The Belgium international even faced the Reds in the Europa League in 2021, getting little change out of Alex Telles in a 4-0 Reds win in Turin, and also starting in the return leg at Old Trafford, in a tie that finished goalless.
Januzaj was part of a La Real attack that contained current Newcastle United hot-shot Alexander Isak.
"I knew, if there were fans here, they would welcome me again," Januzaj told MUTV after the behind-closed-doors match in Italy.