Miami Marlins' Wei-Yin Chen allows a lot of weak contact

The Wei-Yin Chen signing for the Miami Marlins became official a few days ago with the big press conference involving all necessary parties. Chen believes this team is competitive, and his addition should add a win or so to the Marlins' bank this season. However, Chen has performed well in terms of his ERA for years now compared to his numbers based on walks and strikeouts. According to metrics like FIP, which estimate "deserved" ERA based only on true outcomes like strikeouts and walks, Chen has pitched at the level of 4.14 ERA guy for his career. Since 2013, Chen owns a FIP of 4.03, which is about league average in that time span. Compare that to his ERA of 3.61, which is rated as 11 percent better than league average in the same time frame.

According to some of the latest data, it is a possibility that similar such pitchers have some skill in this department. Chen has shown a variety of different possible reasons for pitching above his defense-independent predictors. Some of them are not as predictive as others, but with the advent of data like StatCast, we are starting to understand a little bit more about pitchers and what they can or cannot control. Take, for example, this article by Rob Arthur of FiveThirtyEight from the early parts of the 2015 regular season, the first year in which StatCast was installed in all 30 parks.

The five best pitchers in the league: the Baltimore Orioles’ Wei-Yin Chen (balls leave the bat 1.63 mph slower than average when Chen pitches); the Chicago White Sox’s Chris Sale (1.56 mph); the Los Angeles Angels’ Garrett Richards (1.53 mph); the St. Louis Cardinals’ Adam Wainwright (1.46 mph, before he experienced a season-ending injury April 25); and the Houston Astros’ Dallas Keuchel (1.40 mph).

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Chen is an intriguing case. The best at suppressing batted ball velocity, Chen also has the largest gap between ERA and FIP among qualified starters. In fact, Chen has put up a sizable gap between his ERA and FIP in three of the four years in which he’s pitched in MLB.

When compared to the expected average velocity off of the bat, Chen allowed a velocity 1.6 mph slower almost two months into the season. It is likely that this continued to a degree as well, as Chen's superficial numbers reflect that. Of the 161 pitchers who saw at least 190 at-bats with StatCast installed in the stadium in 2015, Chen's exit velocity ranks 32nd in the bigs at 87.6 mph. Since 2013, Chen has allowed an 18.2 percent rate of soft-hit batted balls, which ranks 14th in baseball, right behind known overachiever Jered Weaver and tied with Jordan Zimmermann.

We do know one reason for Chen's ability to suppress hard-hit balls: Chen induces a lot of pop-ups. Since 2013, there have only been 24 pitchers to post an infield fly ball rate (as compared to all fly balls) of over 10 percent. Chen ranks fifth in that rate, behind only Weaver, Zimmermann, Justin Verlander, and R.A. Dickey. Last season, Chen induced a pop-up in 2.2 percent of his total pitches. Among players with at least 1500 pitches thrown, that ranked sixth in baseball.

Why does Chen do such a good job inducing popups? Eno Sarris of ESPN.com (Insider required but recommended) and FanGraphs pointed it out at the time of the signing: Chen has great command of the fastball in just the right location.

There's a way that Chen uses his command to get that weak contact. His fastball has an inch more rise than the average four-seamer, meaning it falls an inch less than batters expect it to, due to backspin mostly. That movement, plus where he puts it, elicits pop-ups. Look at where Chen throws his fastball to right-handed hitters.

In fact, look at the zone distribution of

Chen throws fastballs high and in fairly often against righties, and that has led to pop-ups at a higher rate than expected, particularly against the more troublesome side. Since 2013, righties have popped up his fastball at a 12.6 percent rate of total balls in play. That means that when the fastball has entered the field of play, almost 13 percent of the time it has resulted in a guaranteed out. The average velocity of these pop-ups in 2015 was 71 mph, which accounts for the big difference in his overall exit velocity and the exit velocities of his grounders and fly balls, both of which were below average.

This points to Chen being someone who allows worse contact when hit squarely but has some ability to manipulate how squarely he gets hit  Pop-ups have decent correlation from year-to-year, though they are not like true outcomes, so there is some measure of skill involved in inducing them. Still, the benefit of inducing them is huge, as pop-ups are essentially equivalent to strikeouts!

However, there is some interest to seeing whether or not there is more to it than that. August Fagerstrom of FanGraphs discussed Chen's varying pitch velocity and considered this as a possibility for why he can allow softer contact than usual. He posted a table littered with high velocity-changes, dropping more than 15 mph between a pitcher's fastest and slowest pitches, and pointed out that other notable overachievers performed this way.

Present in the table is the king of low BABIPs and FIP-beating, Jered Weaver. Alongside Weaver is notorious FIP-beater Zack Greinke, and notorious FIP-beaters Julio Teheran and Shelby Miller, and longtime FIP-beater Chris Tillman, and recent FIP-beater Mike Fiers.

Naturally, this piqued my interest, so I ran some numbers with this group and found that the group, as a whole, posted a soft contact rate of 20%, where the league average is 18.5%, and a BABIP of .286, where the league average is .296. If single-year BABIP doesn’t strike your fancy, the group’s three-year BABIP is .284.

It is possible and logical that Chen's deceptive use of changing speeds could be a good way to avoid solid contact. This may put yet another chip into the "sustainable Chen performance" pile.

Of course, a lot has been said regarding Jered Weaver here, and it should be noted that he has not exactly held up well. Neither has Justin Verlander, who was on the list as one of the most pop-up inducing guys in the game. Zimmermann just signed a large contract, but his previous season represents his worst of his recent career. Heck, even guys like Julio Teheran have not had great seasons recently. It is possible that running this type of skillset is actually higher risk and potentially more likely to decline. We already noted above that when Chen does get hit, he gets hit harder than the average pitcher; with even a small loss in command of that fastball, that balance of pop-ups and blasts out of the park could change. Just ask Weaver of 2011, in his absolute prime:

And his counterpart, Weaver of 2015:

The lack of pitch location in the right areas, specifically in that sweet spot high up in the zone, could lead to the steady increase in home run balls that Weaver has allowed. Combined with an obvious drop in velocity and you have a recipe for disaster.

Chen has to maintain his physical skills and his elite command to keep his FIP-overachieving ways. For the first few years at least, it seems pretty likely, but hopefully it stays that way for the Marlins.