The AL West and One-Run Success

Sunday’s Mariners-Rays game in Tampa Bay ended in memorable fashion, with Seattle right fielder Mitch Haniger failing to make a sliding catch on Carlos Gomez’s bloop, mishandling the ball while attempting to pick it up, but recovering in time to throw home, where Johnny Field, who had been running on contact from first base, was out by a country mile. Catcher Mike Zunino could have paused to make an omelette between receiving the ball and applying the tag:

The play preserved the Mariners’ 5-4 lead and gave them not just their 41st victory of the season but their 21st in games decided by one run. With the Astros also winning, 8-7 over the Rangers, Seattle and Houston remained tied atop the AL West. If you haven’t been paying attention lately, the Mariners — while missing the suspended Robinson Cano and overcoming a 5.70 ERA/4.77 FIP from Felix Hernandez — have spent every day since June 2 with at least a share of the division lead. They’ve done this despite the fact that the Astros have by far the better run differential — the majors’ best, actually:

Now there’s something you just don’t see every day: two teams whose run differentials differ by more than 100 but are basically even in the standings. Those one-run games are the reason. The Astros, who would be on a 109-win pace if they had merely gone .500 in such games to this point, actually won a pair of ’em on Saturday and Sunday, but when it comes to such those contests, they’re still tied for the majors’ fourth-lowest winning percentage and fourth-lowest win total in one-run games. The Mariners, on the other hand, have five more one-run wins than any other team and eight more than any other AL team, though they’re merely third in winning percentage:

Records in one-run games have a lot to do with luck and timing, and it’s rare that a team can sustain a Mariners-like pace over the course of a season. Rare, but not unprecedented: in fact, the two highest season winning percentages in one-run games occurred within the past decade. Here are the top-20 such non-strike seasons since 1901:

These Mariners would be tied for 14th in winning percentage in one-run games if the season were to end today. What’s perhaps more interesting is that, while they’re just about 40% into their season, they’re already halfway to the record for one-run wins:

Both of those lists contain teams that won it all (1907 Cubs, 1909 Pirates, 1940 Reds, 1943 Yankees, 1969 Mets, 1970 Orioles) or at least won pennants (1912 Giants, 1954 Indians, 1959 White Sox, 1980 Royals, 1986 Red Sox), but they also contain teams that didn’t even make the playoffs, such as the 1908 Pirates, 1913 Senators, the record-setting 1978 Giants, and so on — a reminder that eking out a few handfuls of narrow victories isn’t entirely skill-based.

Which isn’t to say skill isn’t involved. Bullpen performance has an outsized effect on a team’s record in one-run games, because unlike on offense, where the batting order may not be at its optimal point(s) at the highest-leverage moments of the game, managers have more control on when to deploy their relievers. In 2016, amid the Rangers’ success, FiveThirtyEight’s Rob Arthur showed a significant correlation (r = .28) between bullpen WAR and winning percentage in one-run games. As it turns out, the Mariners currently rank third in the majors in bullpen WAR (3.3) behind the Yankees (4.1) and Brewers (3.6), two of the teams in their neighborhood in one-run winning percentage. Then again, the Astros are tied for fourth (3.1) — and look where that’s gotten them.

Of course, there’s more to bullpen performance than just WAR, and actual runs allowed — and their timing — both matter. Timing matters in every phase of the game, and it’s worth looking at where the AL West co-leaders stand with regards to our win probability-based Clutch scores, which on an individual level measure “how much better or worse a player does in high leverage situations than he would have done in a context neutral environment.” The Clutch measure compares each player to himself — does he hit or pitch better in higher-leverage situations than overall? — and does a good job of describing the past but not of predicting the future.

On offense alone, the Mariners entered Sunday with four of the AL’s top six offensive clutch scores, with Jean Segura third (0.89), Kyle Seager fourth (0.85), Guillermo Heredia fifth (0.84), and Nelson Cruz sixth (0.83); each has added the better part of an extra win when it comes to Win Probability Added, average Leverage Index (pLI), and context-neutral wins (WPA/LI). At the other end of the spectrum, the Astros’ Carlos Correa (-1.10) ranks fourth from the bottom out of 125 players with at least 150 PA, ahead of only Teoscar Hernandez (-1.11), Mike Trout (-1.32 — it’s tough hitting like Mike Trout all the damn time!), and Giancarlo Stanton (-1.40), with Houston teammate Evan Gattis (-0.69) the 12th-lowest.

Here’s the tale of the tape between the Mariners and Astros:

Of the two teams, the Astros have the slight edge in wRC+, a modest edge in reliever FIP, and a big edge in starter FIP, and yet the Mariners have the better clutch scores on all three fronts — among the AL’s top three in each category, and with an advantage of at least 1.5 wins in each. There’s a whopping nine-win gap between the two teams on this front:

By comparison, the gap between the two teams in our BaseRuns standings is nine games (Astros 44-23, Mariners 35-30) despite their dead-heat actual records; meanwhile, they’re 11 games apart via PythagenPat (Astros 47-20, Mariners 35-30). The last time I checked, however, they don’t determine playoff status via BaseRuns or PythagenPat, and while it’s true that the AL playoff picture already boils down to just six teams (the Yankees, Red Sox, Astros, Indians and Angels being the others — thanks for playing, everybody else!) competing for five spots, it’s also true that the distinction between a division winner and a Wild Card team remains a major one. That the Mariners, despite their holes and flaws (no production at first base, only two above-average starting pitchers, some shaky contributors in the bullpen) are running neck-and-neck with the well-outfitted defending champions — and ahead of the Angels (37-29) — is impressive no matter how they’ve done it. It doesn’t guarantee an end to the longest postseason drought in professional sports, but it certainly hasn’t hurt.