Just over three weeks ago, the future makeup of the Reds roster was something of a mystery. It’s since been resolved for the time being, but the infield is still crowded, and questions about the dynasty league viability of a couple of its occupants are still unanswered.

Coming out of the All-Star break, we knew Christian Encarnacion-Strand was going to have to be promoted at some point. Even with that inevitability, two questions loomed. Where would he play? And which player(s) would have to give way? As it turned out, Encarnacion-Strand had initially been the one to sit more than expected, as he was left out of the lineup three times between his promotion from Triple-A Louisville on July 17 and Jonathan India (plantar fasciitis) being placed on the 10-day disabled list on July 30. India’s injury provided room for all of the Reds regulars to start nearly every game, and now that Jake Fraley (toe) is out, India’s imminent return won’t likely threaten anyone’s playing time.

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The uncertainty was not only a source of some worries for fantasy managers in redraft leagues, but it also had dynasty league implications. Matt McLain and Spencer Steer have had productive rookie seasons, yet some indicators suggest that they have been playing over their heads. McLain currently ranks 12th in standard 5×5 Roto value among shortstops (per FanGraphs’ value calculator), even though he didn’t debut until May 15. Steer ranks 13th at both first base and third base. Yet if we are to believe their xBA and xSLG, as provided by Statcast, we’d have reason to believe they could lose playing time in 2024, if not in the latter portion of 2023.

Whether Encarnacion-Strand merits every-day starts (.258/.310/.379 in 71 plate appearances) or if Noelvi Marte forces his way into a regular role next season, dynasty league managers thinking of keeping McLain and Steer for the long haul should look into the potential risk signaled by those Statcast metrics. But how to embark on that analysis is a whole other question — and one brought to my attention on social media.

@enosarris @DerekVanRiper @almelchiorBB how much weight should we give xStats on Savant? Ex. Savant basically says McLain is due for a pretty steep regression, and here we are 300 PA later.

More generally, how can I use xStats to evaluate expectations vs. reality?

— gilmore.bsky.social (@gilmoreag_) July 31, 2023

While @gilmoreag_ asked only about McLain, I’m offering two analyses for the price of one in this column. I am going to use both McLain and Steer as examples of how we can supplement Statcast xStats with other metrics to shape our expectations for future performance.

Whenever I want to look into the trustworthiness of  a stat for a particular player, I look at the indicators that measure the components that go into that stat. For batting average, that means we need to know how often a hitter makes contact and, when contact is made, how often the quality of contact is the sort that leads to base hits. The frequency of contact part is straightforward, as we can look at a player’s strikeout rate trends (though, if so inclined, you can break that down into swinging strike, called strike and foul ball rates).

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The quality of contact part is more complicated, but a few years back, I wrote some pieces for FanGraphs that aimed to simplify this type of analysis. The “Breaking Down BABIP” series identified the correlates for batting average on ground balls and BABIP on fly balls. The most important factors driving ground ball batting average for hitters were sprint speed and ground ball pull rate. (The analysis covered the seasons from 2015 to 2019, so it remains to be seen if the elimination of exaggerated shifts is affecting the impact of spray angle on ground ball batting average in 2023). Fly ball BABIP was mostly driven by launch angle. As one would expect, high flies in play and popups have a worse chance of becoming base hits than lower flies.

Launch angle is clearly important to slugging percentage, too, and an analysis that Alex Chamberlain and I did for FanGraphs in 2018 showed that average exit velocity on fly balls and line drives (EV FB/LD) was not only among the most highly correlated variables with home run-to-fly ball ratio (HR/FB), but it was also highly sticky from year to year.

These analyses found speed, launch angle and exit velocity to be critical to batting average and slugging percentage — xBA and xSLG take each of these factors into account. For that reason, xBA and xSLG should be taken seriously if they are substantially higher or lower than a hitter’s actual batting average or slugging percentage. Still, it’s helpful to dig a little deeper by looking at more granular statistical measures to see what specific trend, if any, should cause us to doubt a hitter’s actual results. We should also look at a hitter’s pull rates on grounders and fly balls to see if they are possibly impacting their batting average and slugging percentage, respectively.

So, to recap, when we see a discrepancy between batting average and xBA for a hitter, we need to look at:

• Sprint speed (on Baseball Savant’s leaderboard);
• Ground ball pull rate (on FanGraphs’ player splits pages); and
• Fly ball launch angle (on Baseball Savant’s search page).

When we see a discrepancy between slugging percentage and xSLG for a hitter that is substantially larger than the gap between batting average and xBA, we need to look at:

• Ground ball rate (on FanGraphs’ player pages);
• EV FB/LD (on Baseball Savant’s leaderboard); and
• Fly ball pull rate (on FanGraphs’ player splits pages).

As shown in the table below, xBA suggests McLain is hitting 42 points higher than he should be. Even if we weren’t comparing his batting average with xBA, his .407 BABIP would likely raise suspicions about his overall .302 batting average. His average sprint speed is in the 91st percentile, but he has a normal ground ball pull rate (56.8 percent). McLain’s .321 batting average on grounders is 78 points above the major league norm, so speed can only explain so much of that. He is also batting .224 on fly balls in play — 107 points above the major league norm. McLain is hitting fly balls (including popups) with an average launch angle of 40.7 degrees (as compared to the major league average of 42.7 degrees), so once again, he’s profiling as a good hitter on balls in play, but he also looks seriously regression-bound.

McLain’s xSLG is 92 points lower than his actual SLG, and with only 42 of those points accounted for through batting average, the remaining 50 points account for extra bases that xSLG suggests he shouldn’t have had. He is not especially prone to hitting balls in the air (40.7 percent ground ball rate), and when he does, he has average power (93.7 mph EV FB/LD). Aside from luck, there are two other things that could explain McLain’s .522 SLG and .220 ISO. One is a high rate of pulled fly balls, but McLain’s 14.3 percent rate is more than 10 percentage points below the major league norm of 24.6 percent.

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Could Great American Ball Park — the stadium with the second-highest rolling three-year park factor for home runs and fifth-highest for doubles for right-handed hitters — take some of the responsibility for McLain’s power output? He has hit nine of his 12 home runs and 12 of his 21 doubles in home games, and on the road, he is carrying a .425 SLG and .138 ISO. In his 327 career plate appearances to date, sprint speed and park factors appear to be the only variables keeping McLain from being a normal hitter for average and power. This is especially true if he doesn’t carry over his current 24.1 percent line drive rate, and we shouldn’t count on that, since line drive rate isn’t sticky from year to year.

While McLain’s speed and fly ball/popup launch angle make him a candidate to have a higher-than-average BABIP, Steer doesn’t have anything in his profile to suggest that same outcome. Then again, his .308 BABIP is fairly close to normal, though his fly ball-leaning batted ball profile hints at him being a slightly below-average hitter on balls in play. His .247 xBA, in contrast to his .268 batting average, looks spot on.

But what about the more substantial 60-point discrepancy between Steer’s SLG and xSLG? Like McLain, Steer has average power on flies and liners (93.2 mph EV FB/LD), but because he is more prone to hit the ball in the air (35.8 percent ground ball rate), he is not relying on Great American Ball Park for his .463 SLG and .195 ISO. It has also helped that he has pulled 29.9 percent of his fly balls this season. Given that Steer has average raw power, but has a batted ball profile and home park that make the most of that power, it’s hard to see why he would be due for regression, other than a slight dip in batting average.

In breaking down how McLain and Steer have built their stat lines and seeing what Statcast xStats have to say about them, there are a few takeaways.

• Both McLain and Steer have gained some advantage from their home park, but Steer’s batted ball profile indicates that he is less vulnerable to lopsided home/road splits. Barring a drastic change in profile over the season’s final weeks, Steer looks like the better candidate to protect in dynasty leagues.
• Both hitters appear to be safe in their regular roles for the rest of this season, and both have benefited from frequently hitting in the middle of the Reds’ order. If McLain does experience substantial batting average regression in the coming weeks, that benefit could be endangered.
• xBA and xSLG are often useful shortcuts for finding over- and under-performers, but they don’t help us to pinpoint which aspects of a hitter’s profile are responsible for the over- and under-performance. Knowing the parts of a hitter’s profile that aren’t reflected in surface stats enables us to track the most meaningful indicators for signs of progress and make better roster decisions.
• xBA and xSLG also miss the legitimate impact that pull rates and park factors can have on a hitter’s performance.

Note: Season-to-date stats are for all games played through Monday, Aug. 7

Statistical credits: Baseball Savant, FanGraphs, Baseball-Reference

(Kareem Elgazzar-The Cincinnati Enquirer-USA TODAY Sports)