As the New York Mets embark on the 2021 season, we know Edwin Diaz will close, and we know Trevor May can pitch as a set-up man. Past that, this bullpen is a complete and utter quagmire.

Seth Lugo may be out for the first two months of the season. Aaron Loup is a LOOGY. Dellin Betances lost his velocity, and Jeurys Familia still doesn’t have his command.

Robert Gsellman has an 80 ERA+ since being converted to a reliever at the start of the 2018 season. Jacob Barnes has not been good since 2018. Even with his good whiff rates, he gets hit very hard.

After sifting through all the options, you eventually come to Miguel Castro. With Castro, the Mets may have the key to the entire bullpen.

Castro, 25, has been a mediocre reliever in his career as evidenced by his 104 career ERA+. However, that is mostly due to his control issues.

According to Baseball Savant, Castro has elite velocity throwing 98+ MPH. He generates good spin, and, at least in 2020, that led to a lot of swings and misses. That’s also evidenced by his 13.9 K/9, which is nearly double his career 7.4 mark.

The issue for Castro is he just can’t control anything consistently. He has a career 4.7 BB/9, and he hasn’t had a season better than 3.1. His K/BB is a woeful 1.59, and it hasn’t been better than 2.40 over the course of a full season.

It’s not just the walks. Castro gets hit extremely hard. Essentially, Castro puts himself at a disadvantage with his control, which leads to walks and extra base hits. If he can truly harness it, Castro can emerge as dominant a reliever as there is in baseball.

https://baseballsavant.mlb.com/savant-player/miguel-castro-612434

Miguel Castro, Wicked Slider. ? pic.twitter.com/tD2YFyott0

— Rob Friedman (@PitchingNinja) March 24, 2021

On that note, the Mets have helped him and their entire pitching staff. James McCann has emerged as an excellent pitch framer. Tomas Nido is also strong in that department. As we have seen in Spring Training, this has helped Castro not only rack up the strikeouts but also limit walks.

That should help him make quicker work of batters. It should also give him more confidence in attacking hitters. It’s been looking good so far in Spring Training.

In 6.1 innings, he has allowed just two hits while walking just one. He’s also struck out eight batters. Essentially, it’s been difficult for batters to make real good contact against him, and that’s for the batters who can make contact.

If he carries that into the season, Castro can stake a claim as the Mets top reliever. Better yet, between him, May, and Diaz, it’s a six inning game. And, that’s before Lugo returns.

If Castro reverts back to what he’s always been, well, the Mets bullpen is in trouble. That’ll leave Diaz and May as the only true reliable late innings relievers. After them, who knows?

That’s how important Castro is to this team. If he falters, the Mets bullpen is in bad shape. It’ll be a bunch of used to be greats and a group of pitchers hoping someone can break out.

That’s what’s at stake. Castro can single-handedly swing the fortunes of the Mets bullpen. It can be great or less than mediocre depending on Castro’s development. That makes him pivotal to what the Mets want to accomplish this year.

For the Mets sake, they need Castro to be as dominant as he was in the Spring. They need him to be the guy whose light out stuff can shut the door. They need it from him because the Plan B in this Mets organization isn’t there yet or is hurt right now.