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Welcome back to RotoBaller’s Statcast pitcher Studs and Duds article series! Each week I will select an advanced stat, choose two top performers and two under-performers, and analyze what those stats could mean for future fantasy output. This week I will dive into a metric that utilizes exit velocity and launch angle (two metrics we have already looked at) to predict how much damage pitchers should be allowing on batted balls: expected slugging percentage (xSLG).
To calculate xSLG, every batted ball is given a single, double, triple and home run probability based on the results of comparable batted balls. The probabilities for an individual batted ball are then plugged into the SLG formula (1B + 2Bx2 + 3Bx3 + HRx4)/AB to get the xSLG for that batted ball.
xSLG is more indicative of a player's skill than regular SLG because expected outcomes of batted balls are more likely to occur over the course of a season. xSLG removes defense from the equation, which makes sense because pitchers cannot influence what happens to a batted ball once it is put into play. Given its predictive nature, xSLG is an interesting tool to identify potential fantasy steals and guys to avoid. Getting ahead of the game in the buy-low/sell-high market is a valuable way to boost your fantasy team's chances of winning, so I hope you get some helpful trade ideas from this article! I will mix in some relievers for this article as well to help shed some light into the murky waters of bullpens.
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Top xSLG Pitchers
All stats current as of Sunday, May 9.
Shohei Ohtani, Los Angeles Angels
(1-0, 2.41 ERA, 1.39 WHIP, .283 xSLG)
This first player needs no introduction. Shohei Ohtani is a true hitter-pitcher combo threat, which makes him an absolute stud in fantasy leagues. For the purposes of this article, I am going to focus on Ohtani strictly as a pitcher. Now fully healthy, Ohtani has produced solid peripheral numbers to start the season, posting a 2.41 ERA and a .283 xSLG that is 15th-best among qualified pitchers. That being said, fantasy managers have never had a chance to see a huge sample size from Ohtani. Given all the hype that surrounds him, can he live up to expectations for an entire season or is he a potential sell-high candidate (again, as a pitcher)?
The thing that stands out to me right away is that, while Ohtani has a low xSLG, his batted-ball profile leaves much to be desired. His 7.8-degree launch angle is fine, but his 90.6-MPH exit velocity and 42.4% hard-hit rate are both in the bottom third of baseball. It makes sense that he has gotten hit hard as he has left a good portion of his pitches in the middle or top of the zone. Even more puzzling, his 5.01 SIERA supports the hard contact and poor pitch location but does not support his xSLG.
The other concerning aspect about Ohtani's pitching game is that when he is not getting too much of the plate, he isn't getting any of it. His 1.39 WHIP is mostly due to a massive 22.6% walk rate. While it is true that Ohtani does do a good job of avoiding contact overall with a 35.7% strikeout rate, it is also true that a high walk rate can seriously undermine the strikeout rate. I would doubt that Ohtani's walk rate would remain that high over the course of the season, but we only have about 50 career innings to go off of from 2019, so it is hard to say what Ohtani's mark will settle out to be.
Ohtani presents an interesting case in that his xSLG (and other expected stats for that matter) are quite good, but his batted-ball profile, SIERA, and walk rate/WHIP are not. We all know that he can rack up strikeouts, but that won't matter much if his underlying metrics catch up to him. Given the fantasy excitement around his name and the fact that his numbers look good now, I would try to sell-high on Ohtani the pitcher in fantasy leagues in the hopes of getting a nice return.
Craig Kimbrel, Chicago Cubs
(0-1, 5-6 Saves Converted, 0.69 ERA, 0.85 WHIP, .296 xSLG)
No one would have been surprised if I had said that Craig Kimbrel was one of fantasy baseball's best closers a few seasons ago. However, 2019 and 2020 were not kind to Kimbrel, to the point where he dropped off the fantasy radar for a time. He seems to be looking like his old self again, having converted five of six save opportunities for the Cubs this season with a 0.69 ERA and .296 xSLG (among the top-20 in baseball) to show for it. The question fantasy managers may be asking now is, "Should I trade Kimbrel before he devolves back to his 2019-20 self"? My goal is to help you answer that!
Let's first take a look at his batted-ball profile. As his xSLG suggests, Kimbrel has done a good job of avoiding hard contact. His average exit velocity and hard-hit rate are in 76th and 95th percents of baseball, respectively. Specifically, his 87-MPH exit velocity is down from his mark of 91.1-MPH in 2020, and his 26.1% hard-hit rate is significantly down from his 51.9% mark last season.
Further, Kimbrel has done a nice job locating his pitches in order to avoid damaging contact. He has kept his curveball in the bottom of the zone and has kept his fastball out of the middle of the plate for the most part. His location may also be playing a part in helping him avoid contact altogether, as his swinging-strike rate jumped from 12.9% overall last season to 15.7% this season. Finally, his 2.38 SIERA is a good deal higher than his current ERA, but it is a stellar metric either way and supports his xSLG.
I would say the Kimbrel's performance has been legit based on his underlying metrics. He has done a good job of missing bats and has avoided giving up big hits when he has allowed contact. Combine this with his track record of being a great fantasy closer as well as his strong hold on the closer's position and signs point to Kimbrel being a player fantasy managers will want to have on their rosters as the season progresses.
Bottom xSLG Pitchers
All stats current as of Sunday, May 9.
Alex Colome, Minnesota Twins
(1-3, 2-5 Saves Converted, 5.68 ERA, 1.66 WHIP, .664 xSLG)
One of the trickier aspects of fantasy baseball is identifying trustworthy players for saves. Some teams are moving towards a closer-by-committee approach and some are doing away with defined bullpen roles altogether. The Minnesota Twins are one of those teams. That being said, it was assumed that Alex Colome would be the team's primary option in save situations when he signed with the team this offseason. Things haven't gone as planned, as Colome has blown three save opportunities and has the ninth-highest xSLG among qualifying pitchers. He was demoted to lower-leverage situations about a week ago, but the Twins' bullpen situation is still a volatile one. The most important question to answer for fantasy managers is whether or not Colome still has potential value on their rosters.
A quick look presents a pretty bleak picture. All of Colome's expected stats are among the worst in baseball, as are most of his Statcast metrics. He has gotten hit hard, which has not benefitted his xSLG. The interesting thing is that Colome's arsenal has the same velocity and movement as in previous seasons when he was one of baseball's more reliable closers and he does done a good job overall keeping the ball down in the zone. Further, his 4.27 SIERA, while not great, is a good deal lower than his ERA and is not that far off from his career 3.87 SIERA. The final thing that stands out is Colome's BABIP. His .324 BABIP is the highest of his career and is up from his .276 average. It is true that he has gotten hit hard, but I would expect a bit of regression to benefit him over the course of the season.
Overall, I do think that Colome will recover from his poor early-season numbers given his track record and underlying metrics. He seems to be pitching like he has the past several seasons, yet is getting extremely different results. With the Twins' bullpen often in flux, I would guess that Colome will eventually get to see save situations again and could even regain the position as head of the bullpen. The problem for fantasy managers is that Colome offers hardly any fantasy value if he isn't routinely seeing save opportunities. Currently rostered in just 47 percent of leagues, I would say that Colome is worth rostering in deeper roto leagues for now in the hopes that he sees some positive regression in the near future.
Kyle Hendricks, Chicago Cubs
(2-4, 6.23 ERA, 1.62 WHIP, .598 xSLG)
Our final pitcher is one who has had a solid career up to this season. Kyle Hendricks has always managed to find success despite not being an overpowering pitcher, but things have not gone that way this season. Hendricks has put together a poor 6.23 ERA, 1.62 WHIP, and a .598 xSLG that is in the top-25 highest in baseball. While this may be frustrating for fantasy managers, should they give up on Hendricks now?
Taking a look under the hood, Hendricks has not allowed harder contact than usual. His 88.7-MPH exit velocity and 38.4% hard-hit rate are both slightly above average and are in line with his 88.3 MPH and 35.2% career marks. That being said, he hasn't done a great job keeping the ball out of the middle of the plate, so it makes sense that his WHIP and xSLG have suffered. The real culprit behind Hendricks' woes so far has been the long ball. Hendricks has allowed a ridiculous 3.34 HR/9 rate so far this season compared to a 0.96 career mark. I feel like this can only partially be explained by Hendricks' pitch location and bad luck has to be playing a part as well.
Hendricks' peripheral numbers are not encouraging to this point, but there are some potential positives. Hendricks hasn't gotten hit all that hard and his 4.40 SIERA is much better than his current ERA, but he has allowed a ton of home runs (hence his high xSLG). Given his track record, I am holding onto hope that he can turn things around and definitely expect some positive regression in the HR department. As such, I consider Hendricks to be a buy-low candidate for fantasy managers who can afford to have him take up a roster spot while he figures things out.
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