There are two components to the discussion. People tend to focus on the question whether Wright will be any good as a starter. But to decide whether a move is warranted, you also need to ask how Pom would be as a reliever. The question is this: Is Wright as starter and Pom as reliever > Pom as starter and Wright as reliever.
In the end, it’s about run prevention. And outs are outs. In the last five days, Wright has pitched 8 scoreless innings, which is about the most you could hope he would pitch as a starter. If he’s effectively getting 20 outs every 5 days, does it matter that much? At that point, you have to ask whether you get anything out of Pom as a reliever. It’s an unknown. He apparently takes a while to warm up and he hasn’t been a bullpen guy since 2015, when he was ok not great.
He’s also streaky, and we’ve seen that good Pom is very good. The highest upside move is clearly to hope Pom comes around and leave Wright in the bullpen so long as he’s effective.
As noted by others and by Cora himself, he thinks Wright has a chance to be more effective in the bullpen because the contrast is difficult for hitters. Also, there are considerable reasons to think that Wright is much better suited to be a reliever. Looking at game logs over the last couple of years, in any given inning Wright either has it or he doesn’t. When he doesn't have it, he gives up many runs and is not capable of getting three outs and has to come out. It can happen pretty much any time. He virtually never just has a one-run inning. A typical Wright box score is 0 0 0 0 3 (leaves game). When it goes it goes and there’s really no telling when it will happen. Sometimes it’s early, sometimes it’s late. Sometimes he avoids it all game. But it’s pretty rare that he loses it and you don’t have to take him out. Very occasionally, he will limit the damage or someone will swing and miss and take him off the hook and he comes out fine the next inning. But usually, when he stinks he has to be pulled and the inning before isn’t really that indicative. When it happens in the first or second inning and he’s starting, it’s a problem. We’ve also seen that he is possibly susceptible to weather issues. Again, this presents so much more pressure on the bullpen when the starter can’t go. These issues are ameliorated out of the bullpen. There’s less need to stick with a reliever. You can pull him quicker. If Wright starts to lose the knuckler in the sixth inning as a reliever, it's fine -- just get him out and let him pitch tomorrow. When it happens in the second inning, you are tempted to let him ride it out and if he can't your bullpen is screwed. Plus, that's all you get out of him for five days to keep him in line for his next start. Last, since he really doesn’t have a perceptible split, you can bring him in for long relief in pretty much any game – whether he comes in for Sale against an all righty lineup or for Porcello against a lefty-heavy lineup won’t really matter. You’re ok pitching him 2 or 3 innings either way.