Last year, the Miami Marlins were the biggest surprise in baseball, overcoming modest preseason expectations — and an early season COVID-19 outbreak — to not only make the playoffs, but also win a postseason series. Along the way, they needed breakout performances from pitchers (like Pablo López and Sixto Sánchez) and hitters (like Miguel Rojas and Brian Anderson) alike, plenty of perseverance and, yes, an abundant serving of good luck. If not for MLB’s last-second decision to expand the 2020 postseason field from 10 to 16 teams, Miami’s 31-29 record would have left it out of the playoffs on a tiebreaker.1 Furthermore, the Marlins won a lot more than their negative-41 run differential would suggest they “should” have (more on that later). Those fortuitous factors combined to make Miami’s season a success, despite it becoming the first postseason team in MLB history that was outscored by at least a half-run per game during the regular season.
Because of this, though, it was also easy to predict that the Marlins would regress in 2021 if fortune no longer smiled upon them quite as brightly. And sure enough, Miami’s winning percentage has dropped by 64 points, leaving them under .500 (and seven games out of the National League’s final wild-card slot) as we approach the 60-game mark of this year’s schedule. But the drop-off in record has obscured the fact that these Marlins are actually playing much better than they did last season. Instead of putting up MLB’s seventh-worst runs-per-game differential, they now rank 11th-best according to that metric — and that might be underselling how good Miami has been. The main reason for the team’s decline is simply that its remarkable luck from 2020 hasn’t just regressed back to average, it has turned around completely to make the Marlins one of the unluckiest teams in baseball so far this year.
Looking at Miami’s runs scored (263) and allowed (304) in 2020 through the lens of the Pythagorean expectation, we would have predicted the Marlins to have a .434 winning percentage — 83 points lower than their actual mark of .517. Among MLB teams in completed seasons since 1901,2 only the 1905 Detroit Tigers (95 points) and 1981 Cincinnati Reds (87) had a bigger gap between their actual and expected winning percentages. And the gap is even wider (85 points) if we convert wins above replacement3 to an expected winning percentage (.432) and compare it with Miami’s actual record. That difference also landed Miami on the list of biggest gaps ever — so no matter how you look at things, the 2020 Marlins had historic luck on their side:
The 2020 Marlins were among the luckiest in history
MLB teams by biggest difference between actual and expected winning percentages, by run differential or wins above replacement, 1901-2020
|🍀 Luckiest by Pythagorean winning percentage|
|🍀 Luckiest by WAR winning percentage|
In the seasons that immediately followed, these teams tended to see their winning percentages regress back toward .500 faster than we would expect from an ordinary team with the same record.4 So in one sense, it’s not surprising that Miami would be just the latest victim to join that list. But there’s one big difference: According to both Pythagorean and WAR winning percentages, the other teams above stayed roughly steady in their true quality across seasons — in other words, the only thing driving their differences in winning percentage was changing luck. In Miami’s case, however, they have genuinely improved quite a bit since last year.
Although Sánchez and Anderson have been limited by COVID-19 protocols and injuries this season, Rojas and López have been producing WAR at a better pace this year than last year, along with former All-Star righty Sandy Alcántara. (Rojas was also sidelined recently with a fractured finger, so the Marlins will be anxiously awaiting the return of their best position player.) Miami’s position players have gone from ranking 24th in WAR in 2020 to 20th in 2021 — and from 20th to fifth on defense in particular — with big boosts coming from sensational rookie second baseman Jazz Chisholm Jr. and an improved outfield featuring Starling Marte, Adam Duvall and Corey Dickerson. The pitching staff has made even greater strides, rising from 21st in WAR to second — including from 16th to eighth among starters and from 21st to sixth among relievers. Playing at a 6.1-WAR pace per 162 games, lefty starter Trevor Rogers has been the Marlins’ best player as a rookie in 2021, and MLB’s ninth-best pitcher overall.
With a more productive core in place, the Marlins should actually be improving on last year’s record. But in a strange twist of fate, Miami’s luck has gone from historically good in 2020 to historically bad in 2021. This year, the Marlins’ actual winning percentage is 61 points lower than its Pythagorean expectation and 69 points lower than its WAR-predicted winning percentage. If both numbers hold, they would give Miami a place among the unluckiest seasons in MLB history. And no team would have a more painful case of “luck whiplash” than the Marlins, especially in terms of the change in Pythagorean luck from one year to the next:
No team’s luck has collapsed like Miami’s
MLB teams by biggest negative year-over-year changes in luck, by run differential or wins above replacement, 1901-2021
|Pythagorean Luck 🍀|
|Years||Team||Year 1||Year 2||Change|
|WAR Luck 🍀|
|Years||Team||Year 1||Year 2||Change|
(Interestingly, the Toronto Blue Jays of the past two seasons are on the Pythagorean list as well. Somewhat similar to Miami, Toronto is another case of a team that broke out last year and whose middling 2021 record hides a good roster underneath — which they showed the Marlins firsthand in their victory over Miami Tuesday night.)
Despite their complete reversal in fortune, the Marlins are still on the periphery of the playoff chase in the NL East. The injury-ravaged New York Mets are the only above-.500 team in the division, and Miami actually has a better Pythagorean record than any of its division rivals. Although our MLB forecast model gives them only a 4 percent chance to return to the postseason, the Marlins are just close enough to mount a run if they get back to full strength soon. All they’ll need to pull it off is, well, a little luck.
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