The League: Over-and-Under-Performers So Far
The first quarter of the 2021 season is in the books, and the 50th game of the season is about to be played this coming week. The sample size, therefore, has become large enough to analyze who may be outperforming or underperforming so far.
Analysis Process
To ascertain the level over-or-underperformance, a skills-based measure was analyzed versus a standard outcome based metric for both hitters and pitchers.
For hitters, wOBA (weighted on-base average) was compared to xwOBA (expected weighted on-base average) from FanGraphs. The latter utilizes Statcast metrics, such as exit velocity, launch angle and, on certain types of batted balls, Sprint Speed to calculate a skills derived on-base figure.
Per the MLB, xwOBA is more indicative of a player’s skill than regular wOBA, as xwOBA removes defense from the equation. Hitters, and likewise pitchers, are able to influence exit velocity and launch angle but have no control over what happens to a batted ball once it is put into play.
For pitchers, ERA (earned run average) was compared to SIERA (skills interactive earned run average) from FanGraphs. SIERA quantifies a pitcher’s performance by trying to eliminate factors the pitcher can’t control by himself. But unlike a stat such as xFIP, SIERA considers balls in play and adjusts for the type of ball in play.
For each data set, the percentage difference between the two metrics were calculated. For hitters, a negative value means a player that is UNDERPERFORMING what their skills otherwise would indicate (e.g. wOBA for Tommy Pham is 0.287 versus his xwOBA of 0.363).
For pitchers, a positive percentage difference means a pitcher is also UNDERPERFORMING this year compared to what their skills say. (e.g. ERA for Luis Castillo is 7.61 versus a SIERA of 4.40).
Using the percentage differences, a z-score was created to standardize the values and allow for more applicable comparisons. A positive z-score indicates outperformance. Using both the percentage and z-score figures, a team level aggregate was compiled in order to illustrate if a team, overall, is under-or-outperforming skills based metrics — and if there may be some potential for mean reversion.
There a few caveats to this:
- Just because wOBA is higher than xwOBA doesn’t mean one should revert to the other. Yet, it is a fair proxy of where skills do not match output.
- wOBA does not account for all the exact measures of our fantasy league output (i.e. steals, runs, RBI), but it does represent a strong proxy for overall player output considering it combines all the different aspects of hitting into one metric, weighting each of them in proportion to their actual run value
- Similarly, SIERA does not account for all aspects of fantasy value (i.e. K’s, Saves, Wins), but it does show a level of output easily comparable to an actual metric
- This analysis only factors in current rosters and not accrued stats, so the level of any reversion should be factored in based on how the team has been constructed so far
- Only hitters with more than 50 plate appearances were accounted for
- Only pitchers with more than 10 innings pitched were analyzed
- Given the above, small sample size bias for closers can emerge and impact the full team score
- This also doesn’t account for duration of impact (e.g. a SIERA of 4 over 20 IP is less impactful than a SIERA of 4 over 60 innings) in terms of fantasy value
- This is for rosters and stats of the morning of May 24, 2021
Hitters
The team with the biggest outperformance to their skills-based metric is the the last placed Catahoulas Baseball Club. Not a great sign for their team.
The average percentage difference is +2.8% per player, equating to 0.52 standard deviations above the mean — led by Joey Wendle (28%, 0.370 to 0.290), Yuri Gurriel (14%, 0.394 to 0.346), and Nolan Arenado (10%, 0.375 to 0.342). In fact, Joey Wendle is the largest outperformer on a roster.
Beyond the magnitude of outperformance, the depth was also factored in. This was done by calculating the percentage of players on a roster with positive or negative percentage differences — mitigating the impact of outliers. Once again, the ‘Houlas are in first here as well, as 70% of the ‘Houlas hitters are outperforming their skills-based metrics right now.
The next two teams in the top three of outperformance are Dees Nuts and RD Izzo, as shown below. Randy Arozarena had the largest impact to Dees Nuts squad, outpacing his xwOBA by 20% (0.355 to 0.295). Yermin Mercedes (14%, 0.401 to 0.353) and Austin Riley (12%, 0.411 to 0.366) rounded out the top three culprits for Dees Nuts.
RD Izzo has an average player outperformance of 0.4%, led by Byron Buxton (13%, 0.495 to 0.438), Mike Yastremski (13%, 0.339 to 0.299), and Eric Hosmer (5%, 0.343 to 0.326). Half of RD Izzo’s team is outperforming.
The three teams with the potential to “catch-up” to what their skills indicate are Sir Hiss (-5.5%, -0.20, 23%), Dynasty Machine (-4.0%, -0.03, 44%), and the BandBox Baseball Club (-3.6%, -0.03, 22%),
BandBox Baseball Club’s largest underperformer is the newly acquired Tommy Pham (-21%, 0.287 to 0.363). Even if he was removed, BandBox would still be in the top three of underperformance, as Juan Soto (-15%, 0.352 to 0.415) Brandon Lowe (-8%, 0.319 to 0.348), and Ozzie Albies (-8%, 0.344 to 0.374) are still there — as well as others, considering only 23% of the team is outperforming.
Sir Hiss’s underperformance is led by Michael Conforto (-15%, 0.318 to 0.379), Gary Sanchez (-15%, 0.298 to 0.350), and Eugenio Suarez (-13%, 0.251 to 0.290). Only 23% of Sir Hiss players are outperforming their xwOBA.
Dynasty Machine has a higher number (44%of the team), yet their average figure is being pulled lower by Dominic Smith (-19%, 0.270 to 0.334), the third largest underperformer on a roster (behind Tommy Pham and Alex Bohm).
Overall, given the depth of underperformers, Sir Hiss and the BandBox Baseball Club are in a better spot if outcomes start to revert to skills. Meanwhile, the ‘Houlas might be in for a tougher road ahead.
Pitchers
To create combination score later on, pitcher z-scores are inverted. Also, a lower ERA than a SIERA, indicates outperformance. And as of right now, the Wyld Stallyns have the pitching staff with the most outperformance relative to SIERA (-27%, 0.52, 90%). The large difference to SIERA comes from Kendall Graveman, as he has yet to give up a run and his SIERA is 2.48, equating to a 100% difference.
Yet, the Stallyns do have 90% of their staff in an outperformance state, with only Will Smith (31%, 4.5 to 3.4 ERA to SIERA). And if you remove Graveman, the Stallyns are still ranked in the bottom three, as Craig Stammen (-43%, 1.69 to 2.94), Jack Flaherty (-38%, 2.53 to 4.06), and Michael Pineda (-36%, 2.79 to 4.37) are on the roster.
As shown below, the next outperformers are the BandBox Baseball Club (-23%, 0.40, 82%). Once again, it is a reliver skewing the figures. Garret Crochet has a -77% difference (0.71 to 3.07). Additionally, closer committee Tyler Rogers (-65%, 0.7 to 2.0) is also impacting the average percentage figure. However, with 82% in an outperforming state it doesn’t change the overall picture for the BandBox.
Marcus Stroman and Kevin Gausman are both outperforming their metrics (-30%, 2.73 to 3.92 and -42%, 1.66 to 2.87). Yet, Corbin Burnes is underperforming his SIERA (1.79 to 1.29), buffering the impact from the other starters on the team.
Rounding out the bottom three is RD Izzo (-21%, 0.34, 82%), led by large deviations from Aroldis Chapman (-75%, 0.47 to 1.9), Mark Melancon (-58%, 0.84 to 1.98) and John Means (-46%, 1.7 to 3.14).
In terms of teams that are underperforming their expected SIERA, Blazzin Buffalo Chickens, Sir Hiss, and Dynasty Machine rank in the top three. For Blazzin’ Buffalo Chickens, their team is being held back by weak output from two closers (Rafael Dolis +45% and Rafael Montero +54%) in addition to Jesus Luzardo (+56%).
Sir Hiss’s figures are also inflated due to closer activity, as Matt Barnes has a +114% difference (2.42 to 1.14). Yet, their starters are also contributing. Eduardo Rodriquez (+48%, 5.06 to 3.43) and Aaron Nola (+31%, 3.94 to 3.00) are impacting the teams aggregate score. Not to mention 50% of Sir Hiss is underperforming their SIERA right now — the second most amount of underperformers in the league (behind Dynasty Machine).
Dynasty Machine is being plagued by Luis Castillo (+73%, 7.61 to 4.44) right now, as no other pitcher is above a +20% mark. However, 46% of his team is underperforming. But just not by much. If we remove Luis Castillo, Dynasty Machines numbers are not that terrible, in the aggregate.
Overall, closers are skewing the results here. But there does seem to be some true starter underperformance with Sir Hiss. And some outperformance from BandBox Baseball Club.
Z-Score Combination
Given the standardized nature of z-scores we can combine both the hitter and pitcher analysis into a one team combination score, illustrating what team may be underperforming overall. As shown below, Sir Hiss has the most to gain if his players to start to perform up to their true potential, followed by Dynasty Machine and Blazzin’ Buffalo Chickens. Conversely, RD Izzo might not want to order the nameplate for the Okrent Cup just yet.
For those interested, the data for this analysis can be found below
