3. Jon Niese
Making his MLB debut with the Mets in 2008, Jon Niese was a promising young pitching prospect with a wicked 12-6 seam curveball and solid fastball velocity. As fans, we all saw flashes of great potential throughout Niese's 9-year Mets career. In 2012 and 2014, Niese pitched to a 3.40 ERA across 30 starts each season, which is quality enough to be a mid-top of the rotation starter. We saw flashes of a dominant left handed weapon out of the bullpen during the 2015 postseason having gotten big outs against the Dodgers and Cubs.
Although Niese showed glimpses of a high-end starter, his inconsistency made him another disappointing Mets prospect. His 2015 regular season was lackluster, pitching to a 4.13 ERA across 29 starts. This was not enough to keep him in the picture for 2016 with the Mets having the big 5 in deGrom, Harvey, Matz, Syndergaard, and Wheeler already on the staff. After committing to Bartolo Colon for the 2016 season, Niese was dealt to Pittsburgh for Neil Walker.
Why did Mets fans never embrace Jon Niese? It was the disappointment of never living up to the blue-chip prospect ceiling he was given in 2008. Niese never seemed to find that consistency and became an every-other year solid starting pitcher. Once the Mets developed the young arms, Niese's rotation security was in jeopardy. He didn't have the fan gravitating personality of Bartolo to save him after the 2015 World Series. In remembering the early 2010's, Niese was a good Met that just never hit his ceiling. Beyond that, I never minded his comments after being traded either, saying "I can't wait to pitch in front of the Pirates defense". Let's be honest- defense cost us the 2015 World Series.