Pitchers Most Impacted By Defense: OAA Fallers

Eric Samulski looks at the new Statcast OAA defensive metric and uses it to analyze which starting pitchers were helped most by their defenses during the 2019 season.

Early in January, Statcast released a full fielding leaderboard of their Outs Above Average (OAA) metric, which had previously been limited to outfielders only. The metric takes into account fielder positioning, reaction time, throw difficulty, and batter speed in order to calculate how likely a play is to become an out. The more unlikely, the more points a fielder will get for converting the out and the fewer he'll lose if the play winds up becoming a hit.

There's a more detailed breakdown of it here, but essentially it aims to tell us just how good a fielder is and just how many potential outs he recorded over the norm.

Does this new metric have any impact on fantasy baseball? Perhaps we can find a way to evaluate the stickiness of the metric or see just how much we should be using it when projecting pitching value for a given season.

The Lucky Ones (Pitchers with High OAA)

Now that all infielders have been charted on this metric what can be extrapolated out of that is just how much a certain pitcher benefitted from elite defense behind him. In their own words, Statcast can track "the performance of the defense behind the pitcher while he was on the mound." The higher the recorded OAA when a pitcher is on the mound, the more outs his defense recorded that likely shouldn't have been outs based on the average outcome. The lower the OAA is for a pitcher, the more his defense gave away outs that should have been converted on average.

This alone isn't enough to determine if a pitcher is good or bad or if their 2019 fantasy season was real or fluky; however, placed in a larger context, it can tell us which pitcher's stats may have been the result of their own changes, defensive skills, luck, or perhaps a grouping of the three.

Since this metric is relatively new when it comes to its impact on pitching, I decided to dig into a few names from the top and bottom of the leaderboard just to see if there was anything to take away. I'm thinking aloud here or, more precisely, typing as I go, so feel free to take a look at the Statcast Leaderboard yourself and see what stands out to you.

Dakota Hudson (SP, STL)

No pitcher was helped more by his defense in 2019 than Hudson. When he was on the mound, the defense recorded 16 OAA, which was double the next highest mark in the league. Since that second-highest mark was set while teammate Miles Mikolas was on the mound, it's safe to say that the Cardinals infield performed well last year. In fact, if you look at the OAA leaderboard, Paul DeJong finished seventh overall, Kolten Wong finished 13th, Matt Carpenter was 25th, and Paul Goldschmidt was 33rd. If Carpenter's myriad injuries were to act up, Tommy Edman would be only a slight downgrade, as he finished 48th overall. Hudson's extreme groundball tendencies - 56.9% - and low SwStr% - 9.8%- make him overly reliant on his defense, so when he gets well above average help like he did last year, he can succeed.

However, regression is coming. Not necessarily because the defense will get worse behind him, but because he's a clear outlier in OAA. If he even gets the defense his teammate Mikolas did, it would negatively impact his overall numbers. The fluky nature of Hudson's season is also backed up by his 3.35 ERA despite a  4.55 xFIP,  his relatively low .274 BABIP and high 40% Hard Hit%. They all suggest that tougher days are ahead.

Merrill Kelly (SP, ARI)

In his first year back stateside after a turn in Japan, Merrill Kelly had some intriguing runs of starts where he showed a plus fastball and the ability to stifle an offense. However, OAA suggests that he was fortunate in the modest success that he had, and the defense behind him in 2020 may have taken a step backward.

With the addition of Starling Marte, Ketel Marte has been shifted to 2B permanently, which is great for the Diamondbacks offense, but worse for the defense as Ketel Marte had a 5.6 UZR in the outfield but only a -1.3 at 2B. Also, a look at Kelly's contact profile hints at possible regression. Kelly's 85.1 Z-Contact% and minuscule 12.7% soft contact suggest that batters are frequently touching him up when he's in the zone. Without the same level of defense behind him, he could be looking at a worse season, so it's best to tread carefully in drafts.

Lance Lynn (SP, TEX)

Lance Lynn is an interesting case. He benefited from the fourth-highest OAA in the league, which indicates that defense played a role in his success; however, Lynn's GB% dropped over nine points and his SwStr% rose 2.5 points as he dialed back on his sinker. The new pitch mix led to decreases in both O-Contact and Z-Contact and a 5.1% increase in K%, which simply means that batters are making less contact against Lynn and he needs his defense's help less than in year's past. However, it's foolish to think that the defense provided no benefit.

Almost half Lynn's OAA seems to have come due to outs above average laterally towards 3B. That could be because of Elvis Andrus' defense, which got him ranked 34th overall on the OAA leaderboard, but it also could be because of the defense of Asdrubal Cabrera, who played 93 games at 3B for Texas and had a UZR of 3.4. When he was traded, Danny Santana (0 UZR) and Nick Solak (-3.2 UZR) saw the majority of the innings. This season, it appears likely that Solak or Todd Frazier (-1.2 UZR) would see the majority of innings at 3B, which could lead to weaker overall defense for Lynn. I just don't think he was as reliant on these defensive metrics as some of the other names on this list, so I wouldn't expect it to impact his final stats too much.

German Marquez (SP, COL)

Marquez's presence on this list isn't surprising. He's changed his pitch mix, adding more sliders and sinkers and relying less on his fastball, in order to increase his GB% each year of the last three years as a way to balance the effect of Coors Field's altitude. There are also four Rockies in the top 30 of the OAA pitcher leaderboard - tied for the most of any team. In fact, Nolan Arenado ranked second overall in the OAA leaderboard, while Trevor Story finished a few places behind in fifth. Both players also registered elite UZR numbers - Nolan Arenado finishing at 10.3 and Trevor Story at 8.6.

Despite the above-average defense, Marquez's season-long numbers still suffer due to playing his home games at Coors, where he's been unable to prevent batters from lifting his pitches. His home/road splits last year are awful. 3.67 ERA on a .212 BAA and .273 wOBA on the road, and a 6.26 ERA on a .317 BAA and .356 wOBA at home. If the Rockies' fractured relationship with Nolan Arenado leads to a trade, it's going to make the defense noticeably worse and hurt Marquez and all other Rockies pitchers' outlooks for 2020

Aaron Nola (SP, PHI)

One run behind Marquez and Lynn on the leaderboard are two interesting names: Aaron Nola and Sonny Gray. Nola is a groundball-heavy pitcher whose GB% has hovered around 50% in each of his Major League seasons. Last year the main difference was that his Zone% dropped 5% and his F-Strike% dropped to 7%, which meant he fell behind in the count often and allowed hitters to see more favorable situations and better pitches, causing a .045 point jump in BABIP and an almost 17% rise in Hard Contact.

If Nola regains his control and regresses more towards his career averages then he might see even more benefit from his defense this year now that he's trading in Maikel Franco (-.1 UZR and 133 OAA) for Scott Kingery (4.5 UZR and 74 OAA). I'd be inclined to buy into Nola, not shy away.

Sonny Gray (SP, CIN)

I have a little more pause regarding Sonny Gray's presence on this list. The right-hander experienced a resurgence last year due to a change in pitch mix. He abandoned his cutter altogether, which is good since it had a negative pVAL, and relied more on fastballs and a slider that saw a 10.4 jump in pVAL. His SwStr% rose 1.2% but his contact metrics stayed relatively similar, including allowing slightly more hard contact and less soft contact.

The changes in pitch mix were nice to see, but it also seems like he benefited from having OAA's ninth-ranked overall fielder Jose Iglesias (5.9 UZR) start at shortstop behind him. While Freddy Galvis isn't a major drop-off, his career UZR suggests that he doesn't match Iglesias' dependability, and Gray will also have Mike Moustakas play second base once Eugenio Suarez comes back. Moustakas has only played one season at the pivot and registered a -.1 UZR. Some of Gray's pitch mix changes signal real evolution, but the worse defense behind him is slightly concerning for a pitcher who saw his BABIP fall from .326 in 2018 to .255 in 2019. I'd expect some regression there, which likely means an ERA closer to last year's xFIP of 3.65.

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