It's difficult for a defender without game time to come in and play 90 mins and be perfect. With that in mind thought he did well. If he could get a run of games free of injury he'd gain in confidence and we'd see a different player I reckon.
I'm sorry but this has been said time and time again. I am not trying to single you out personally, because a few people have expressed that opinion, but there are two fundamental factors to contend with here that undercut the point you are making:
(1) If he can get a run by staying injury free - It's just a very big IF isn't it? His injury record, just like the legendary sick note Phil Jones, is pretty horrendous; and history shows us that it would be enormous folly to rely on him being consistently available. If you do what you've always done, you'll get what you've always gotten; and with Bailly, it's been injury setback after injury setback. It would be a huge risk, and frankly unforgivably negligent, to build a defensive unit around his consistent participation.
(2) If he gains confidence he'll be a different player - History has also shown us that while Bailly can produce some top class performances, including a measure of outstanding athleticism and defensive prowess, he always follows it up - within a few games - with a calamitous performance. A performance as ludicrously bad on the scale, as his more sublime efforts can be at the other end of the curve. He has never consistently performed to a high level, even when fit for a decent duration, while being in a United shirt. He has shown potential to be a quality CB, but has always allowed an undercurrent of rashness, lapses in concentration, or just outright shiteness to bleed through eventually.
With both these things in mind, I cannot possibly imagine how we can realistically ever see him as anything more than a stop gap, bit part player, potentially useful in rotation; but also the footballing equivalent of playing Russian Roulette.
For us to be realistic title contenders, we need two CBs that are consistent in both their fitness and performances. For the first time in ages we have that in Maguire and Lindelof, which is undoubtedly our best partnership. What is missing is that we need a little more quality. We either need Lindelof to build on his extended run in the side and take another step up, or we need to replace him with someone who can offer the same consistency he does, but play at a significantly higher level. Thelast thing we should be doing in my opinion, is to go backwards and start relying on high potential, but incredibly unreliable CBs. One of the most important qualities of a defensive unit is familiarity and consistency.