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The Mariners Offense Is Seriously Underperforming

A look at the early season struggles of the Mariners offense.

Kansas City Royals v Seattle Mariners Photo by Steph Chambers/Getty Images

On Tuesday, the Mariners were shutout for the sixth time this season. That matches the number of scoreless games the Oakland A’s have posted this year, tied for most in the majors. Maybe that isn’t all that surprising given how poorly Seattle has played recently — four of those shutouts have come in May. Here’s the weird thing: the A’s have the worst wRC+ in baseball at 79, but the Mariners have been one of the better hitting teams in baseball with their team wRC+ sitting at 110. Yes, the Mariners have been slumping recently, but this goes beyond their annual springtime swoon; they’ve been seriously underperforming their underlying offensive metrics and it’s costing them plenty of winnable games.

Missing Mitch Haniger from the middle of the lineup has really hurt in May, and getting little to no production from Jarred Kelenic, Luis Torrens, and Abraham Toro hasn’t helped either, but there are enough guys producing at a good clip to be reasonably confident in this lineup. Their team wRC+ backs that sentiment up too. Here’s a look at where they rank in a variety of offensive categories so far this year.

Mariners Offensive Metrics

BABIP BB% K% ISO wRC+ RS/G
BABIP BB% K% ISO wRC+ RS/G
Mariners 0.277 9.7% 21.8% 0.14 110 3.84
MLB Rank 21st 6th 12th 17th 9th 21st

Despite a wRC+ that sits ten percent above league average, they’ve only scored 3.8 runs per game, one of the worst marks in baseball. The key to the Mariners offensive success has been their ability to get on base regularly via free passes while avoiding striking out too much. Their power output has been right around league average too. The biggest problem with the team’s current approach is a reliance on getting positive results on their balls in play; right now, their batting average on balls in play is well below average and forms one of the biggest reasons why they aren’t scoring as many runs as you’d expect.

Last year, the Mariners overcame a negative run differential with ridiculously excellent performances in nearly every clutch situation they faced. They had the most clutch offense in recorded MLB history (WPA records only go back to 1974), which goes a long way toward explaining the team’s 33–18 record in one-run games last year. (Their bullpen, obviously, helped in that regard too, but they managed only the 12th most clutch performance in MLB history.) This year, the Mariners have been rather average when the game is on the line, with a clutch rating exactly in the middle of the table (0.24 Clutch, 15th in the majors). Similarly, in high leverage situations, the Mariners have been right around league average with a 94 wRC+.

Their lack of production when the game is on the line doesn’t really explain why they’ve underperformed so drastically. To dig a little deeper, let’s turn to a concept I’ve written about a fair number of times: cluster luck. Teams who cluster their baserunners and hits together usually score a bit more than expected while teams who scatter a bunch of solitary hits won’t score as many runs as you might expect. We can use the BaseRuns formula to estimate run scoring based on the number of baserunners, how many of those baserunners advanced, and the number of outs created. Then we can compare actual results to come up with a tangible measure of how “lucky” a team has been.

Mariners Cluster Luck

Month Run Differential Expected Run Differential "Luck" Offensive "Luck" Pitching "Luck"
Month Run Differential Expected Run Differential "Luck" Offensive "Luck" Pitching "Luck"
April 16 19.21 -7.60 -5.56 2.35
May -27 -23.94 -3.06 -9.02 5.96
Overall -11 -4.73 -10.66 -14.57 8.31

As you can see above, the Mariners have underperformed their expected run differential nearly the entire season so far, but that difference has been really exaggerated during their May swoon. Their actual run differential is six runs lower than what you’d expect based on the number of baserunnners they’re getting on base and allowing. But even that figure is a bit misleading. The Mariners offense has underperformed by a whopping 14.5 runs — in other words, they should have scored an additional 14.5 runs simply based on the number of baserunnners they’ve produced. Unfortunately, because of the way they clustered those walks and hits, those 14.5 runs never actually materialized. Only because of some better than expected pitching have they kept their expected run differential so low.

The good news is that cluster luck and clutch hitting are backwards looking metrics — they tell us what happened in the past but don’t really have much predictive value. The Mariners have a good offense that’s been a bit unlucky recently, but all the underlying metrics tell us that they should be scoring runs at a much higher clip than they have been. With the hardest part of their May schedule behind them, it’s likely they’ll see those results come through.

A couple of notable details from the data:

  • The Mariners have played six games where their expected run differential was positive despite actually losing the game. Four of those hard luck losses have come in May and two of them happened during that four-game series against the Rays at home. The other two occurred last week — the final game against the Phillies and the second game against the Mets.
  • That series against the Mets was all sorts of wonky. In the two games the Mariners won, their expected run differential was negative, meaning they were lucky to walk away with victories.
  • The unluckiest game of the season so far was their 8-6 loss against the Rangers on April 21. The Mariners made three errors in that game and left 12 runners on base, leading to a -3.44 difference between their expected run differential and the actual two-run loss.