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Miami Marlins right-hander Eury Pérez recorded his first career quality start on Wednesday against the Seattle Mariners, throwing six shutout frames, striking out six batters and permitting just three baserunners. Through seven big-league outings, he's sporting a 1.80 ERA and 2.6 strikeout-to-walk ratio. Not bad for someone who will not celebrate their 21st birthday until next April.

Pérez's brilliance is one contributing factor to the Marlins' second-place standing in the National League East. (Their majors-leading 17 victories in one-run games, however unsustainable that may prove to be, is another.) As such, we wanted to highlight one of the game's most exciting and -- with each passing day drawing us a step closer to the postseason -- important rookies.

Here are three factors that help explain Pérez's quick ascent. 

1. Good heater

The late Tom Seaver once said the most important pitch is the fastball, and that the second most important pitch is also the fastball. 

Times have changed since Seaver's declaration. These days, it's more permissible for a starter to use his secondaries frequently, even to the point where they serve as his primary pitch. Seaver's overarching point still has validity though. Consider Pérez. He doesn't use his fastball as often as Seaver would've -- he throws about 46% heaters, making it his bellcow but not to a predictable extent -- yet it's certainly the engine that makes his arsenal go.

Pérez's fastball is a high-grade pitch. He sits around 97 mph and he's one of just nine MLB starters this season (min. five starts) to clear 100 mph. Factor in his ability to get down the mound, resulting in a deeper release point, and his heater has an effective velocity closer to 98.5 mph. The pitch isn't just coasting on its speed, either. Pérez's fastball features more than 17 inches of induced vertical break. Some pitchers with similar verticality and release heights on their fastballs include Zac Gallen, Gerrit Cole, and Julio Urías.

Pérez hasn't yet started to miss bats with his fastball -- his whiff rate checks in at a below-average 13% -- but the swings and misses figure to come at some point. To wit, FanGraphs hosts pitch-modeling data that attempts to gauge the quality of each individual pitch based on their attributes. Pérez's fastball ranks 18th (out of 491 qualified pitchers) with respect to its "stuff" qualities. That puts it on par with the likes of Spencer Strider and Jacob deGrom's fastballs. 

Of course, you needn't know or care about the model to conclude Pérez has a promising fastball. It's not his only good pitch, either.

2. Arsenal depth

While Pérez hasn't evaded much lumber with his fastball to date, he's made up for it by dodging bats with his secondary pitches. He has three other offerings he throws more than 10% of the time: a pair of breaking balls and a changeup. The lowest whiff rate generated by those three pitches is 38%. 

One of the interesting things about Pérez's secondaries is how much they benefit from a newer concept called seam-shifted wake. Essentially, it's the idea that certain pitches can move in an unexpected way because of how the seam orientation interacts with the air, creating an optical illusion to hitters

If all that sounds too nerdy and obscure … well, fair enough. Just know that Pérez generates at least 15 degrees of deviation between his spin-based and movement-based break on all three of his secondaries. That means, in layman's terms, that his arsenal has a lot more deception in it than you'd think. Add that to his pure power, and you have something special brewing.














Pérez's success is based largely on what he's throwing, but there's also the matter of who he's throwing to -- and we don't mean Miami's catchers.

3. Quality of opponent 

We've spent the entire piece praising Pérez, and for good reason. He's an extremely talented youngster with a bright future. We do feel obligated to note that he hasn't quite faced top-flight competition throughout his first seven starts.

Indeed, take a look at Pérez's opponents so far as well as where they rank in runs scored and wRC+, a catch-all metric hosted at FanGraphs that accounts for ballpark among other variables:

















White Sox






That's seven starts, and only one of them against an above-average offense, at least as judged by wRC+. Contrariwise, he's faced a bottom-third offense on five occasions, and the 19th-ranked offense on a sixth. 

Pointing this out isn't meant to take anything away from Pérez, either. You can pitch only to the schedule you're given. Nevertheless, it is a factor in assessing why he's dominated the way he has. 

Pérez is certain to face steeper competition in the near future: his next start is slated to come against the Toronto Blue Jays (fifth in wRC+) and his start after that will be line up for the Pittsburgh Pirates (14th). We suspect he'll find a way to rise to the occasion, and that he'll remain a big part of whatever success the Marlins have -- this year and those to come.