Depending on which version of Wins Above Replacement (WAR) you prefer, St. Louis Cardinals reliever John Brebbia either had a great rookie season (1.1 bWAR) or an essentially replacement-level one (0.1 fWAR). Of course, the disparity, in admittedly very rough terms, is due to bWAR looking specifically at runs allowed as opposed to fWAR using FIP. Brebbia's ERA was fantastic last season (2.44; 20th in MLB), while his FIP (4.13; 108th in MLB) was underwhelming. Hence, the noticeable disparity between the two value measures.
Yet, no matter how you choose to look at it, given the expectations prior to his late-May promotion, it's hard to complain about Brebbia's performance in 2017. Minor league rule five selections infrequently pan out, and the mere fact that Brebbia played a legitimate role on the big league club should be considered a mission accomplished. Plus, his performance last season was successful enough to be considered a viable bullpen option going forward. That is, if he is able to maintain -- but preferably build on -- the success he had in 2017. As we all know, relievers are volatile. Young relievers are even more volatile, as opposing teams work tirelessly to create a scouting report despite such a small sample size.
Well, two of my favorite Twitter follows -- @stlfanbc7 and @SenorBush -- asked me -- this site's so-called "pitching analyst" -- to look closer into Brebbia's rookie campaign. Was it for real? Could he build on it? Or is he due for some serious regression? Of course, we must first revisit the concept of reliever volatility, but I still feel like you can find interesting information when digging through PitchF/x data on BrooksBaseball.net and Statcast data on BaseballSavant.com.
Individual pitch results (via BrooksBaseball)
Remember, I try not to overstate the value associated with individual pitch results. Sequencing is not taken into account when you look at only the last pitch of an at bat. Did the slider induce a whiff because it was sequenced and tunneled well by a sinker on the pitch prior? Or was the whiff a result of the slider's inherent nastiness? Was a fourseamer hit into Big Mac Land because it doesn't have the makings of a good pitch overall or was it because the batter was just thrown four straight breaking balls and he simply guessed right on getting something hard and straight?
Even with this in mind, it is impossible to ignore batting averages below .200 on not only one but a pitcher's two primary pitches. As you can see, Brebbia is essentially a fourseamer (52.15%)-slider (40.70%) pitcher. As a reliever, this type of repertoire can work -- especially considering Brebbia's average fourseamer velocity (94.54 MPH). Now, batting average is far from the best hitting measure, but still, from a pitching standpoint, anywhere under .200 is impressive nonetheless. That being said, look at the last column: BABIPs in the low .200's are hardly sustainable.
While Brebbia did induce a high rate of swings and misses with his fourseamer (at 26.11% whiffs per swing), the pitch was still put in play on 31% of swings (when you exclude the 42.86% foul ball rate). This is where Baseball Savant comes into play. Remember how I said there are better hitting measures than batting average? Well, wOBA is one of them (FanGraphs primer). In 2017, Brebbia's fourseamer yielded a wOBA against of .304 (league average: .354)-- which is great! However, his xwOBA -- which takes into account contact quality -- was .343 (league average: .344), suggesting the pitch is due for some serious regression.
Add in average exit velocity and launch angle, and one will become even more worried. The average exit velocity versus a Brebbia fourseamer last season? 91.5 MPH, or 3,3 MPH faster than the league average. The average launch angle? 23.3°, which may be on the high-end of line-drive (10-25°), but when coupled with an average exit velocity north of 90 MPH, is more in line with the popular "flyball revolution."
Remember, whenever analyzing relievers, the sample size is small, particularly when looking at one specific pitch within one specific season. Thus, three batted balls could have a not-insignificant effect on a given pitch's results. Below, I asked @cardinalgifs to .gif up three fourseamers thrown by Brebbia last season. While all three led to outs, a glance at the respective exit velocities shows us the batted balls could have been considerably more damaging.
Middle-middle fastball to Trey Mancini
(Let's use this pitch as a learning experience for all. StatCast classifies the pitch as a fourseamer, while BrooksBaseball -- and rightfully so, in my opinion -- classifies it as a sinker. Regardless, it's middle-middle, and if launched correctly, the result could have been much worse.)
Middle-middle fourseamer to Adrian Gonzalez
Middle-down fourseamer to Nick Franklin
Instead of overvaluing three admittedly cherry-picked pitches, let's instead take a fairer look at Brebbia's approach with the fourseamer. I know I bring the following up frequently, but I do because it just makes so much sense. Eno Sarris is the very best pitching analyst the internet has to offer, in my opinion. And he speaks of "command" in the sense of throwing pitches in tough-to-hit locations. Well, as you can see below, Brebbia did a terrific job at "commanding" his fourseamer last season. His two most populated zones yielded the lowest average exit velocities (80.8 MPH, 82.0 MPH).
Thus, while Brebbia's fourseamer xwOBA signifies regression, we at least know his overall location was solid. If he is able to clean up his location even more, his fourseamer will remain an effective pitch for him, especially when sequenced/tunneled with the slider (the average vertical release points between the two pitches vary by less than three-fourths of an inch) .
In fact, let's talk about that slider a little bit. Not only did it yield a batting average below .200, but it also rendered opposing hitters powerless, to the tune of a .136 isolated power. The wOBA against? A downright amazing .250, and unlike what we saw with the fourseamer, the expected wOBA (or xwOBA) -- .256 -- was largely in line with Brebbia's actual results. As is the average exit velocity against of 82.7 MPH (league average: 84.9 MPH). Thus, where there was some cause for concern with Brebbia's fourseamer, I just don't have the same concern with his slider. Sure, he's bound to experience some batted ball misfortune, but he can play his part in limiting the damage by inducing whiffs (31.29% whiffs per swing) and soft contact.
Popout by Wil Myers
Strikeout of Starling Marte
Strikeout of Charlie Blackmon
(I included this slider to show that the pitch can be a weapon versus lefties -- even some of the league's very best lefties.)
Bottom line
All things considered, Brebbia far exceeded any reasonable expectations set for him last season. Honestly, the fact that he provided any value at the big league level at all is impressive. Yet, with success comes higher expectations. Now, don't be unreasonable and expect him to all of a sudden become a 40+ save closer. But at the same time, don't write Brebbia off as a "one season wonder." He has a solid reliever repertoire that tunnels quite well (this is a hint toward a follow-up post). Yes, I strongly believe the Cardinals need to add another arm to the bullpen, but at the same time, they shouldn't also forget about what Brebbia brings to the club.
As always, credit to @cardinalsgifs, BrooksBaseball.net, BaseballSavant.com, and FanGraphs.com for their respective contributions to this post.