Even With Their Co-Aces Back, the Mets’ Rotation Needs a Depth Reset

After a doubleheader sweep against the Guardians Sunday, the Mets have stretched their winning streak to five and stand two games above .500 for the first time since May 3. In the double-bill, co-aces Justin Verlander and Max Scherzer combined for 14 innings while allowing just one run. Granted, they mowed down the league’s worst offense by wRC+, but for fans, the pair’s dominance was a sight for sore eyes: Verlander missed all of April with a shoulder issue and Scherzer has had to work around a sticky-stuff suspension, a neck issue, and general ineffectiveness this year. Given these obstacles, it’s reasonable to wonder whether Sunday represented the turning point fans were hoping for or a mere blip in a season of decline for the veteran hurlers. To protect against the latter, the Mets will have to take a hard look at their starting pitching depth.

Coming into the season, we ranked the Mets starting staff as the second-best in the league, right behind the Yankees. While the Bombers have had to weather some injuries of their own, their starters have still managed to post an above-average WAR, FIP, and ERA. Head across the city to Queens, though, and you’ll find the second, third, and sixth-worst staff by WAR, FIP, and ERA, respectively. Clearly, the problems aren’t limited to their top two starters.

Due to ailments of their own, the Mets have gotten just 18.2 frames out of José Quintana and Carlos Carrasco combined. But one reason we liked the Amazins’ staff so much to begin the season was their enviable depth — their sixth, seventh, and eighth starters in David Peterson, Tylor Megill, and Joey Lucchesi easily could have started the season as part of the top-five somewhere else. The three of them have all been healthy, and along with Kodai Senga and the (inconsistent) contributions of Scherzer, that alone should have made for a serviceable starting five through April.

Senga has held his own, and we don’t have to re-hash Scherzer’s struggles, but the other three depth players have been disappointing. Megill, whose 3.88 ERA masks ugly peripherals and ERA estimators all north of 5.00, is the only one remaining in the rotation. The estimators are similarly pessimistic about Lucchesi’s performance despite a decent 4.43 ERA. And then there’s Peterson, with rosier peripherals but an atrocious 8.08 ERA. The Mets need to keep the latter two stretched out in the minors, but if they didn’t, there probably wouldn’t be a place for them, even in a bullpen that is also below average by WAR, FIP, and ERA. I’ll give Lucchesi somewhat of a mulligan since he missed all of last year due to Tommy John and is still getting his legs under him, but can the Mets tweak the other two hurlers to ensure they have a better cushion for the stretch run? Or is it too early to suggest that the team peruse the trade market?

Let’s start by taking a look at the one pitcher in the trio due for at least some positive regression — Peterson. There’s just no way he’ll continue to run an exorbitant .404 BABIP, an enormous 25.0% HR/FB ratio, and a paltry 58.8% strand rate; these marks rank second-highest, third-highest, and fourth-lowest among the 128 pitchers with at least 30 innings this year. He’s also posting a career-best groundball rate and near-best K-BB%, which is why SIERA and xFIP like him so much.

At the same time, that BABIP may remain somewhat elevated as long as he continues allowing career-high barrel (9.8%) and hard-hit (43.4%) rates. Those two marks are in the 26th and 25th percentiles, respectively, this season. As a result, his xERA of 5.19 is in the 22nd percentile.

What explains the batted-ball results? As things stand right now, the first four seasons of Peterson’s career have alternated between good and very poor. Those numbers track with his luck indicators, yes, but they’ve also tracked with the results on his slider:

The slide-piece has always been Peterson’s go-to non-fastball, but he’s also never thrown it more than 30% in a season. It’s interesting that the pitch seems to make or break his whole repertoire; the Mets may have sensed that as well, and decided to make it more of an establishing pitch this year (a tip I received from my friend James Schiano at Mets’d Up). Peterson has thrown 44% of his sliders in even counts and 45% of them in the zone this year, both career highs.

On his career, Peterson’s slide-piece has cost him 8.2 runs in even counts and saved him half a run in all others. Similarly, the pitch has cost him 7.1 runs in the zone and only 0.6 outside of it. This year has been no exception:

It’s worth noting that he’s thrown it harder than ever this season while his fastball velocity has dropped a tick, narrowing the gap between the two pitches. The movement is also tighter, with an inch and a half less induced horizontal break. Perhaps the Mets encouraged Peterson to throw the tighter slider, and throw it for strikes more often. Perhaps the move to the new slider was inadvertent, and it’s only been in the zone more often because the drop in horizontal break has kept it from dropping off the plate. Yet another possibility is that the Mets, seeing how much better last year’s slider was in the zone (bucking the trend for Peterson’s career), told him to throw it for strikes but didn’t anticipate the movement being tighter. Whatever the case may be, the pitch is not working, with career worsts in CSW% (29.6) and barrel rate (15.6%) in addition to run value, so we might see a different slider if he’s recalled.

When it comes to luck, Megill has been the opposite of Peterson this season, running career bests in BABIP (.278), HR/FB ratio (12.2%), and strand rate (79.2%). His 8.6% barrel rate is a career low, which explains some of the BABIP improvement, but he’s still handily outperforming his 6.04 xERA. That astronomical number is probably because of his weak 6% K-BB rate, eighth-worst among the 104 pitchers with at least 40 innings this season. It seems pretty clear that if he wants to keep his ERA below four going forward, something will have to change.

Like Peterson, Megill’s primary breaking ball has also been going through changes. Unlike Peterson, his slider has lost a couple ticks and become bendier; it’s lost about an inch of horizontal movement but gained over an inch and a half of drop. Like Peterson, the result has also been a career-worst CSW% and barrel rate; the only reason it has saved Megill a run rather than cost him many is because hitters have underperformed their xwOBA on the pitch by over 100 points. Megill has also lost a tick on his fastball this season, so at least the slower slide-piece maintains the velocity separation. But the new shape probably isn’t doing him any favors.

On the other hand, there might be an easier fix for Megill than Peterson; while the new slide-piece doesn’t seem too inspiring, his new curve does. He’s throwing it just over three ticks slower, but the deuce has gained a massive amount of movement — four inches of drop and around three inches of horizontal break. It’s notched a career-high 31.3% CSW and a .177/.193 wOBA/xwOBA, albeit with just eight balls in play on record. Despite the small sample with the curve, it’s hard to argue in favor of that slider at the moment; there’s little to lose in trying the curve as Megill’s primary breaking ball.

If we choose to view Megill’s breaking ball tweaks as purposeful too, it’s easy to see how they align strategically with Peterson’s. The tall left-hander had a much better slider than fastball last year, so the Mets figured a tighter slider could be the solution to setting hitters up. Megill, on the other hand, has gone to his four-seamer over 50% of the time each season he’s been in the majors, and for good reason. Though he’s lost some velo on it this year, he still has 98th-percentile extension, which makes its speed play up. Peterson has 95th-percentile extension, but his heater is slower and doesn’t have the arm-side run Megill’s does; he’s tried a sinker too, but it’s been his worst pitch by run value on his career (its shape is also different this year, possibly reducing the mirroring effect between it and the slider). The bottom line is that when it comes to Megill, the Mets are content to have him continue to rely on his fastball as a setup pitch, and have moved to make his breaking balls more whiffy. The strategy hasn’t worked for his slider, but his curve could be transforming from an afterthought into a legitimate weapon.

Assuming they aren’t accidental, I can understand why these changes came to fruition. But it’s clear that Peterson and Megill both need more workshopping, the kind that should probably be done in the minors. Unfortunately, the Mets will be stuck with at least one of them at the major league level until July, when Quintana is set to return. For the time being, Megill will hold Quintana’s spot, and his solid ERA has made him a more palatable option for fans. Just don’t expect it to be solid going forward unless more changes come to pass.