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Who’s Good And Bad In MLB This Year? We Don’t Really Know.

Rewind just a few years, and one of the big themes in baseball — in addition to the ever-present concerns about a juiced ball, greedy owners and games taking forever — was a serious lack of parity between the best and worst teams in the game. In 2019, MLB’s most recent full season, a record four teams cracked 100 wins while four teams also failed to win 60 games (and the dreadful Detroit Tigers didn’t even reach 50 wins). Thanks to a combination of rampant tanking by bottom-feeders, the efforts of a previous generation of tankers yielding big results and an increased ability for savvy big-market clubs to press all their advantages, the chasm between baseball’s top and bottom clubs had seldom been wider. 

After a shortened pandemic season in 2020, however, MLB’s competitive balance seems to have reset itself for 2021. Through Sunday’s games, only one team — the resurgent Boston Red Sox — is on pace for at least 100 wins, while two — the Colorado Rockies and the Tigers — are on pace for fewer than 60. Meanwhile, 15 teams are bunched between a 77-win and 90-win pace, and 19 teams have between a 20 percent and 75 percent chance of making the playoffs, according to our MLB forecast model. We’re still early in a schedule that normally takes every bit of its 162 games to distinguish good teams from bad ones, but it seems like we know less about who fits those categories this season than usual.

One quick way to measure how much parity baseball has seen this year — relative to the same stage of previous seasons — is to look at the standard deviation of winning percentages. Through 34 games for each team,1 that number is 0.0747, meaning one standard deviation below .500 lands you on a pace of 69 wins per 162, while a standard deviation above .500 puts you on pace for 93 wins. That may sound relatively ordinary, but early season records usually vary a lot more than that. Through 34 games in 2018, for instance, one standard deviation below .500 would have put a team on pace to win just 60 games, while a standard deviation above .500 meant winning at a 102-victory pace.

Granted, the 2018 season was one of the most imbalanced in MLB since 1969, the start of the divisional era. But 2021 is shaping up to be one of the most balanced. Only in 1974, when just one team (the 102-win Los Angeles Dodgers) won more than 91 games and just three won fewer than 70, did a season start with as much competitive balance as 2021, according to the standard deviation of winning percentages through 34 games:

This year has seen the most parity in a long time

MLB seasons with the lowest and highest standard deviation of team winning percentages through 34 games per team, 1969-2021

Most parity Teams on Pace for…
Season St dev of WPct >=95 wins <=65 wins Sum
1974 0.073 2 1 3
2021 0.075 5 3 8
1980 0.078 5 3 8
1989 0.083 5 2 7
2011 0.083 5 3 8
Least parity
Season St dev of WPct >=95 wins <=65 wins Sum
1981 0.145 8 7 15
2018 0.131 9 7 16
1988 0.129 7 5 12
2003 0.127 8 5 13
1977 0.125 8 5 13

For 2021 teams with more than 34 games played, only the first 34 games were considered for the sake of consistency.

Source: Retrosheet

A big reason is that the teams that looked most dominant on paper going into the season have gotten out to slow starts. Remarkably, each of the top nine teams in our preseason Elo ratings has seen its rating dip since then; only the 10th-ranked Toronto Blue Jays have exceeded expectations in the early going:

Most of the predicted top teams have been ‘meh’

Top predicted 2021 MLB teams (according to FiveThirtyEight’s preseason Elo ratings) and their change in Elo since opening day

2021 Record
Team Preseason Elo Wins Losses WPct Current Elo Diff.
Dodgers 1599 18 17 .514 1590 -9
Yankees 1572 18 16 .529 1562 -10
Padres 1561 19 16 .543 1557 -4
Astros 1552 18 16 .529 1550 -2
Mets 1540 16 13 .552 1537 -3
Twins 1538 12 20 .375 1520 -17
Braves 1534 17 17 .500 1527 -7
Rays 1533 19 17 .528 1532 -2
Nationals 1520 13 17 .433 1515 -6
Blue Jays 1519 17 16 .515 1527 +8

Those teams haven’t been bad, mind you.2 But with a collective record of 167-165, it’s fair to say they have not been as good as advertised. And at the other end of the spectrum, seven of the bottom 10 teams in preseason Elo have gained rating points since opening day, headlined by the surprising San Francisco Giants — as they retool impressively from the end of their dynasty era — and the somehow-above-.500 Seattle Mariners. As a result, last year’s winning percentages explain only 13.6 percent of the variation in this year’s winning percentages after 34 games, the lowest mark for MLB at the start of a season since 2016-17.3

Gleyber Torres is tagged out while trying to steal second during an April game against Baltimore. The Baltimore player’s glove is hitting him in the face, while a referee stands off to the left.

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Cold as they have been recently, the defending-champ Dodgers still top our forecast; the model thinks the Dodgers will turn it on and win 98 games before all is said and done. (And for what it’s worth, they’ve played much better than their middling 18-17 record would indicate.) But this parity-laden first 20 percent or so of the 2021 schedule has served to tighten the predicted records for most teams in our model. Fully half of the league is now forecasted to have a win total in the 80s, which could make for some really interesting decisions around the trade deadline and into the playoff race down the stretch run.

For now, though, it’s strange to watch some of baseball’s theoretical best teams scuffle, posting records no better than teams that looked a lot worse on paper going into the season. Whether that’s been due to leftover effects from the pandemic season, changes to the ball or something else entirely, parity does appear to be back in baseball after years of trending in the opposite direction.

Check out our latest MLB predictions.

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  1. The average team has played 33.7 contests so far in 2021.

  2. Well, most haven’t. The Twins’ pitching might beg to differ.

  3. When 2016 records explained only 2.6 percent of the variation in 2017 records after 34 games. It wasn’t really surprising that year, though: At the height of the tanking trend, we might expect that to be true if tanking were working, leading bad teams to suddenly become good.

Neil Paine was the acting sports editor at FiveThirtyEight.