Mets' bullpen is better than you think, but Shintaro Fujinami and Jorge Lopez could determine its ceiling

The 2023 Mets were done in by a lot of things, including their lack of starting pitching depth, Starling Marte playing hurt all season, and poor situational hitting.

But of all the things that befell New York, it was the loss of star closer Edwin Diaz that seemed to hurt the most.

Fresh off one of the best seasons any reliever has ever had, Diaz re-signed with the Mets on a massive five-year deal last offseason. He was again going to be the backbone of the bullpen, and the player who -- more than anyone else -- was the emotional center of the team and fan base.

Diaz of course never set foot on a big league mound in 2023, with a freak knee injury while celebrating one of Puerto Rico's wins in the World Baseball Classic robbing him and the Mets of the entire year.

The loss of Diaz turned David Robertson from setup man to closer, and caused a ripple effect throughout the rest of the relief corps.

And during the month of June, when the Mets went from 30-27 to pretty much out of contention, they lost eight games by one run -- something that almost certainly would not have happened if they had Diaz anchoring the bullpen.

But Diaz is now back at full strength, already unleashing his vaunted fastball/slider combo during live batting practice sessions at spring training as he prepares for the 2024 season.

That Diaz is the only proven elite reliever expected to be in the 2024 bullpen will mean the rest of the group needs to step up.

And while the 'pen -- like the starting rotation and lineup -- has several question marks, it's probably not getting enough credit.

Sep 9, 2023; St. Petersburg, Florida, USA; Tampa Bay Rays relief pitcher Jake Diekman (30) throws a pitch against the Seattle Mariners in the sixth inning at Tropicana Field.

Here's how it could look on Opening Day:

Edwin Diaz: CLS
Brooks Raley
Adam Ottavino: RHP
Jake Diekman: LHP
Drew Smith
Jorge Lopez
Shintaro Fujinami: RHP
Michael Tonkin or Phil Bickford

Beyond the likely members of the bullpen are a number of depth options, including Grant Hartwig, Reed Garrett, Sean-Reid Foley, Yohan Ramirez, and Josh Walker.

Before we talk about the potential upside of a bullpen that could be sneaky good if a few things break right, it's important to note that the Mets are projected by many as a fringe playoff contender due in part to a small margin for error.

And that small margin for error is not only something they'll have in the rotation and the lineup (where the Mets will need Brett Baty and/or Mark Vientos to step up and must get a return to form from Marte), but in the bullpen.

If Diaz were to miss significant time again, things would be thrown into disarray. The same goes for long-term absences for Raley or Ottavino.

But excepting health, the group David Stearns has assembled should at the very least be solid. And if just one of Stearns' high-ceiling signings pans out, it would give the Mets a potential shutdown arm who could transform how the end of games look.

Those two high-ceiling signings, who could be true X-factors for the Mets in 2024, are Fujinami and Lopez.

The downside?

Lopez is coming off a season where he had a 5.95 ERA and 1.50 WHIP combined for the Minnesota Twins, Miami Marlins, and Baltimore Orioles, and his career numbers are uninspiring: a 5.51 ERA and 1.48 WHIP in eight seasons.

Fujinami made his big league debut in 2023, and had unsightly numbers for the Oakland Athletics before being traded to the Orioles, where he improved but was still below average -- a 4.85 ERA in 29.2 innings.

Sep 5, 2023; Anaheim, California, USA; Baltimore Orioles relief pitcher Jorge Lopez (73) is relieved against the Los Angeles Angels during the seventh inning at Angel Stadium.

The upside?

Presently, Fujinami and Lopez are not high on the pecking order -- behind Diaz, Raley, Ottavino, Diekman, and Smith. But they possess the stuff to be late-inning arms. Lopez has been one before, and it was recent.

In 2022, Lopez was an All-Star during a season with the Orioles and Twins where he had a 2.54 ERA and 1.18 WHIP while allowing just four home runs in 71.0 innings. His ERA+ was 155.

That season, Lopez's Baseball Savant page was like a work of art, with him near the top of the league in most categories, including barrel percentage, hard hit rate, and ground ball rate.

His stuff -- featuring a fastball that averaged 98 mph to go along with a curve, changeup, and slider, was tremendous as hitters slugged .331 or worse against his fastball (sinker and four-seamer) changeup, and curve.

Lopez featured a similar arsenal in 2023, but in looking at his heat maps, his changeup and slider were catching way too much of the plate. And his four-seamer (which was mostly at the letters in 2022), bled into the middle of the zone way too often.

As far as Fujinami, he throws even harder than Lopez, with a fastball that can reach 103 mph.

The key for Fujinami going forward will be knowing where his pitches are going. He walked 5.5 batters per nine in 49.1 innings last season for the A's, bringing that rate down to 4.6 per nine with the O's.

And toward the end of the season, Fujinami had a 12-game stretch where he was locked in -- posting a 1.35 ERA over 13.1 innings while walking two and striking out 16.

One thing that could help Fujinami with the Mets is that he'll be working in relief full-time instead of being in the hybrid starter/reliever role he was in last season, when he had a 14.26 ERA in seven starts and 5.14 ERA in relief.

While the ERA in relief isn't great, some of that was likely due to bad luck, with Fujinami holding hitters to a .209/.319/.351 triple slash and drastically improving his strikeout/walk rate out of the bullpen.

In a world where Fujinami and Lopez struggle, the floor of the Mets' bullpen won't change that much, with them possibly replacing one or both with one of the depth options mentioned above or via the trade market.

But if Fujinami and/or Lopez excel, the Mets will be adding another high-impact arm or two to the late innings, drastically raising the bullpen's ceiling.