Lost in the discussion about whether Michael Wacha should be in the starting rotation or bullpen is whether or not he is capable of being successful in the bullpen.
In 2019 with the only organization he's ever known, the Cardinals, Wacha struggled as a starting pitcher and ended up being moved to the bullpen. Unfortunately, he got rocked in the bullpen as well, ending with a 5.68 ERA (6.37 FIP) and a 1.82 WHIP during a sporadic 13 innings.
The way it stands, based on reports and reading between comments often made by Luis Rojas and Brodie Van Wagenen, it seems Wacha will end up most often pitching in long-relief and be the first person called upon when the Mets urgently need a fill-in starting pitcher.