According to the Italian outlet Il Romanista (via The Sun), the former United manager failed in his pursuit to land the Ivorian last month but is planning a summer swoop.
Bailly was signed in 2016 under Mourinho for a fee of £30 million.
He was expected to be the backbone of United’s defence for years to come, but was unfortunately hampered with multiple injuries.
He has made just four appearances for United so far this season, hence a move away makes sense.
Bailly’s contract expires in 2024 and Mourinho is keen on re-signing him.
AS Roma are currently struggling defensively and Mourinho is desperate to add reinforcements in the summer.
Bailly’s physicality and pace would be an asset to the Serie A team.
Mengi has impressed so far in his loan spell at Birmingham City and could be a future star at United.