Under Mourinho, Bailly made 40 PL starts, 5 sub, unused sub 10 matches. But after his ankle injury, the respective numbers were 8 PL starts, 4 sub, 7 unused sub.
Under Solskjaer, Bailly has made 11 PL starts, 6 sub, unused sub 28 matches. Transfermarkt state that he has been injured for a total of 61 PL matches since joining United.
He was a first choice starter until his ankle injury. Our defensive record with him in the team was generally good for the first 18 months and astonishing during 2017. I thought he struggled to regain his form after the ankle injury. Then an extended period out after knee surgery, allowed Lindelof and Maguire time to establish a partnership.
Anyway, Bailly has to choose between playing time, which he is likely to get more of elsewhere, and the higher salary he would probably earn staying at United.
At the moment, he is a good option to use for specific matches, rather than a serious contender for a regular starting position, though if a vacancy arises due to injury, then he might be able to force his way into the team.