Guess What? The Mets' bullpen is really good, and the advanced numbers prove it

Coming into the 2021 MLB season, the Mets' bullpen -- without Seth Lugo -- was viewed as a bit of an unknown, though there was plenty of promise when it came to the back end.

Would it be average? Would it be a true strength?

Then, after the bullpen imploded during a season-opening loss to the Philadelphia Phillies, we wrote that until Lugo is back, managing the 'pen will be a balancing act.

While it still has been a bit of a balancing act due to a heavy reliance on Edwin Diaz, Miguel Castro, and Trevor May, the bullpen has been largely dominant.

Just how good the Mets' relievers have been has (understandably) gotten lost in the shuffle a bit due to the team's inability to hit the baseball early this season.

But if you expect the Mets' offense to eventually snap out of this maddening funk, New York -- with a bullpen that has been stellar and mostly great starting pitching (with Carlos Carrasco and Noah Syndergaard on the way) -- could immediately become a very dangerous team.

Let's break down just how good the key cogs in the bullpen have been...

Edwin Diaz

We told you before the 2020 season that what happened to Diaz in 2019 was an aberration and that he was due to bounce back, which he did.

And we told you before the 2021 season that Diaz was dominant and reliable, which he has been.

So how he's pitched so far this season should not be a surprise.

In nine innings over nine appearances, Diaz has a 2.00 ERA (1.98 FIP) and 1.00 WHIP with 11 strikeouts and just three walks (one of which was intentional). And a glance at Diaz's page on Baseball Savant shows a hell of a lot of red (which is a good thing).

Diaz is among the best in baseball when it comes to hard hit percentage, strikeout rate, barrel percentage, chase rate, expected ERA, expected SLG, and exit velocity allowed.

Miguel Castro

We surmised before the season that the Mets' bullpen could become a real strength if Castro harnessed his elite stuff, and that's exactly what has happened.

Castro, acquired via trade last season, has become a dominant force in relief and the Mets' most relied on option aside from Diaz.

Controlling a fastball that touches 100 mph to go along with a plus changeup and slider in the low 90s, Castro has been a revelation.

Castro has a 2.25 ERA (0.34 FIP) and 1.25 WHIP with 14 strikeouts (15.8 per 9) in eight innings over eight appearances.

Trevor May

May allowed two runs in his first appearance of the season, and has reeled off seven scoreless appearances in a row since then while starting to rack up strikeouts in prodigious fashion.

He looked as good as he has all season on Wednesday night against the Boston Red Sox, striking out the side.

May, whose advanced metrics have been mostly elite so far this season, has a 2.45 ERA (0.36 FIP) and 1.22 WHIP with 13 strikeouts (16.0 per 9) in 7.1 innings over eight appearances.

With May and Castro dominating to go along with Diaz, the Mets haven't really missed a beat without Lugo, whose return should make the late innings even more treacherous for opposing teams.

Aaron Loup

With all of the Mets' electric arms, it's a bit surprising that Aaron Loup is the only reliever of the bunch here whose ERA is literally zero.

The left-hander has yet to allow a run in 4.1 innings over five appearances this season, while striking out five and walking none.

He will continue to be a key piece going forward, especially when the Mets face the big lefty bats of the Philadelphia Phillies (Bryce Harper), Atlanta Braves (Freddie Freeman), and Washington Nationals (Juan Soto).

Jeurys Familia

The shocker of the bunch is Jeurys Familia, though I guess it shouldn't be too surprising considering the success he's had in his past and his still-elite sinker.

Like May, Familia hasn't allowed a run since his first appearance of the season, notching six straight scoreless outings since.

Overall this season, Familia has a 1.59 ERA (2.03 FIP) and 1.58 WHIP with six strikeouts in 5.2 innings over seven appearances.

Given how good Diaz, Castro, May, and Loup have looked -- and with Lugo likely returning at some point in May -- what Familia has done has been gravy in a way. But the Mets will gladly take it.