The former Everton defender was once let go by David Moyes.
The likes of Barcelona and Real Madrid have also been linked with the player, with Bayern Munich also keen. But The Express have reported on Mustafi being on Manchester United's radar. The 23-year-old has a £37 million release clause in his deal and United need to bring in some new blood at the heart of defence.
The interesting aspect to this potential deal regards the German international's past - as a David Moyes reject.
Whilst the former Everton boss was not wanted by Manchester United, Mustafi was not wanted by Moyes at Everton.
Everton snapped up the youngster from Hamburg in 2009 and he played just one game for the club against BATE Borisov in the Europa League.
But by January 2012 Moyes had decided Mustafi would not cut it in the Premier League and let him join Italian side Sampdoria on a free transfer.
Since then he has come on leaps and bounds and helped Germany win the World Cup in Brazil last summer.