In some ways, Steven Matz resembles the rest of the Mets' postseason rotation. He's young. Of the three other starters, only Noah Syndergaard is his junior. He also throws hard. While his fastball velocity is just a tick behind Matt Harvey and Jacob deGrom, it's still impressive, averaging nearly 95 mph.
In other ways he's very different. First of all, Matz is the only left-hander in the Mets' postseason rotation. He's also much less experienced against major league hitters. Although Matz and Syndergaard are both rookies, thanks to a series of injuries, Matz has pitched just 45.1 big league innings in his career, both regular and postseason. That's about a quarter of Thor's workload despite being called up just a month and a half later.
His regular season results, however, were brilliant. Matz posted a 2.27 ERA, but across just six starts. His peripherals painted a slightly less glowing picture, but his FIP was still slightly above league average at 3.61. With Syndergaard waiting in the wings at the beginning of the season, non-Mets fans can be forgiven if they weren't familiar with Matz before his debut, although he did have the pedigree that suggests that his results this season reflect substantial talent.
Matz' track record of health, on the other hand, left much to be desired. His first injury was a big one, a lat tear that put him on the shelf for two months. He returned from that injury only to leave his first start early with a blister on his left hand. He ended the season hurt again, this time with a lingering back issue that nearly kept him off the postseason roster against the Dodgers.
If Matz was a bit lucky in the regular season, it's been the opposite in the playoffs. He's allowed 4 runs in 9.2 innings for an ERA a full run higher than his FIP. He's only faced more than four batters in an inning once, and allowed just two extra base hits, both doubles. In each of his starts, Collins has given him the quick hook, but likely to spare his back, rather than for his performance.
Like most pitchers, Matz leans heavily on his fourseasm fastball, throwing it about two-thirds of the time. He experimented briefly with the famous Dan Warthen slider, but he's shelved in the last two starts in favor of his changeup, a pitch he threw a season high 15 percent of the time to the Dodgers and Cubs over his last two starts.
Despite the small sample size of big league innings, Matz has had predictable platoon splits, faring much better against right-handers (wOBA of .278) than lefties (.315). He's attacked the former with the changeup (24%) while the latter get more breaking balls (29%). Matz' curveball is still looks like a work in progress, though he has said that he feels more confident with the pitch than ever before.
A big part of the Mets' success this year, particularly in the postseason, has been the ability of their starting pitchers to get swings and misses. Each of the other postseason starters have boasted swing and miss rates of 13 percent or greater across all their innings this season. This is another area where Matz differs from his rotation mates, as he's gotten swinging strikes on just 9 percent of his pitches. Tonight is a prime opportunity for the Royals to do what they do best, put the ball in play and continue to test the Mets' defense. Tonight, they'll do it against a pitcher who hasn't appeared in ten days. Matz, however, is used to these long layoffs. They just usually come because he's been hurt.