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The Mariners bullpen and the long ball

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The HR/9 rate of the Mariners bullpen was much higher in September than it was during the rest of the year.

Dan Hamilton-USA TODAY Sports

Baseball is over, and while awards, free-agency, and rampant trade speculation loom as we move forward into the offseason, I'm not quite ready to forget about 2014. The Mariners were so close last year!

On the one hand, 2014 was somewhat of a wonderful surprise. Even with the splashy signing of Robinson Cano, expectations for this team weren't terribly high, and it was wonderful to be able to savor meaningful baseball until the last day of the regular season. Alternatively, sometimes I feel like it's hard not to view 2014 as a big ol' missed opportunity. Maybe this is overly pessimistic, but in a season where there were no truly dominant teams, it's a damn shame that the Mariners weren't able to muster a .500 record over their last 20 games to sneak into the playoffs. With their rotation, it was pretty easy to envision the Mariners making a deep run in October... if they'd just been able to get there. Anyway, dwelling on the what-ifs and the if-onlys is a fruitless pursuit and is only going to make me feel lousy. Instead, I wanted to take a closer at their performance over the last month of the season to look at what might've gone wrong.

The team faltered in a lot of ways down the stretch (hitting, starting pitching, and relief pitching). However, while I was looking at the numbers, something that jumped out at me was the massive increase in the bullpen's HR/9 rate over the last few weeks of the season. In the month of September, over a span of just 21 games, the Mariners bullpen gave up 12 home runs. Before September 4th, they'd given up 12 long balls in their previous 83 games. This is a very large difference, and I was curious as to how  much all of those dingers may have hindered Seattle's chance of making the playoffs. Breaking down the bullpen's month-to-month performance, I put together the following table:

Month Innings K/9 BB/9 K/BB HR/9 AVG WHIP BABIP LOB% ERA FIP xFIP SIERA
April 81.2 8.49 4.63 1.83 0.77 0.232 1.40 0.288 76.7% 3.42 4.05 4.00 3.82
May 74.2 9.52 3.38 2.82 0.60 0.225 1.23 0.294 81.8% 2.65 3.13 3.29 3.01
June 76.2 8.80 2.23 3.95 0.23 0.182 0.89 0.245 83.6% 1.64 2.37 2.71 2.44
July 83.0 8.67 3.04 2.86 0.54 0.196 1.05 0.250 82.4% 1.84 3.18 3.35 3.01
August 87.0 9.72 2.69 3.62 0.52 0.209 1.08 0.279 81.3% 2.38 2.75 3.20 2.73
September 97.0 9.09 2.97 3.06 1.11 0.241 1.27 0.296 79.9% 3.43 3.83 3.38 3.01
M's 2014 498.1 9.07 3.12 2.90 0.65 0.216 1.15 0.277 80.7% 2.60 3.24 3.32 3.01
MLB avg. 487.1 8.46 3.29 2.57 0.78 0.238 1.28 0.294 73.9% 3.58 3.60 3.67 3.34

It should be noted that the Mariners bullpen did pitch the most innings in September; it might make sense for the raw number of home runs allowed to increase; however, their HR/9 rate increased as well. At the end of August, Seattle's bullpen had a HR/9 of just 0.53. That would've rated as the fourth best home run rate for a bullpen in the last 20 years. After a bumpy September, the M's ended with a HR/9 of 0.65, which is still quite good: the 24th best bullpen since 1995 and the fourth lowest in franchise history. Running such a low HR/9 rate throughout the first several months of the season suggests that regression would likely be forthcoming as the season continued; this certainly appeared to be a contributing factor toward the spike in home runs allowed by the Mariners 'pen in September.

Looking at some of this data graphically can help us visualize trends a bit easier than just looking at a big ol' table:

bullpen month-to-month

For the y-axis in this plot, I've normalized the numbers for each month by dividing them by the season-long averages (e.g., the HR/9 for September, near 1.75, shows that the HR/9 for this month was ~75% higher compared to the season average HR/9).

Here, we can see a very sharp increase in the home run rate during the last month of the season. This undoubtedly contributed to an increase in the number of runs allowed; however, none of the other peripherals (e.g. walk and strike out rates) really varied too far from the season averages. BABIP/BA numbers did rise in September, suggesting that Seattle's pitchers may have had slightly less good "stuff" or that they were slightly less lucky, but the overall number of baserunners that they allowed didn't increase by too much.

Their stats in March/April were a little inflated by the fact that Luetge and Noesi made five combined appearances, giving up more than 16% of the bullpen's runs in the month despite logging only 4% of the innings pitched. However, once they'd settled upon their preferred seven relievers towards the end of April (or eight, once Maurer converted to relief), they were very consistent between May and August (with the exception of their performance in June, which was just bananas). And then September happened. While the wheels certainly didn't fall off, the bullpen's performance certainly dipped significantly.

In addition to regression, it's possible that fatigue was an issue. A lot of players are known to run down as the season progresses and although the Mariners had one of the better rotations in baseball, Lloyd still went to his relief corps a bit more than average. Despite the eight-man bullpen, these relievers weren't under-worked.

Name G IP K/9 BB/9 HR/9 BABIP LOB% GB% HR/FB ERA FIP xFIP WAR
Tom Wilhelmsen 55 75.1 8.12 3.70 0.72 0.200 86.0 % 52.1 % 10.3 % 2.03 3.68 3.59 0.2
Danny Farquhar 66 71.0 10.27 2.79 0.63 0.298 79.2 % 41.8 % 8.8 % 2.66 2.86 2.94 0.9
Fernando Rodney 69 66.1 10.31 3.80 0.41 0.330 77.5 % 48.6 % 6.3 % 2.85 2.83 3.14 1.2
Dominic Leone 57 66.1 9.50 3.39 0.54 0.282 83.3 % 54.7 % 9.5 % 2.17 3.07 3.07 0.7
Yoervis Medina 66 57.0 9.47 4.42 0.47 0.298 82.0 % 53.3 % 7.9 % 2.68 3.45 3.59 0.3
Joe Beimel 55 45.0 5.00 2.80 0.80 0.250 86.8 % 49.6 % 9.5 % 2.20 4.18 4.17 -0.2
Charlie Furbush 67 42.1 10.84 1.91 0.85 0.327 75.4 % 35.5 % 9.3 % 3.61 2.80 2.83 0.7
Brandon Maurer 31 37.1 9.16 1.21 0.24 0.283 75.1 % 39.4 % 2.2 % 2.17 1.85 2.99 0.9

The average qualified reliever in MLB pitched about 62 innings in 2014. Four Mariners relievers pitched more than that, but none of these eight gentleman set a new career-high for the number of innings pitched (if you count minor league numbers). This, of course, doesn't mean that fatigue wasn't a factor, but nobody was pitching in uncharted territory.

And even if fatigue wasn't a direct cause for the decrease in production, the fear of fatigue may have been a contributing factor. Lloyd may have been trying to spread out the number on innings pitched in an attempt to prevent his relievers from running down so that they'd still be effective if his team made the playoffs. With all of the September call-ups, Lloyd had more arms to pick from out in the 'pen. The eight men listed in the table above pitched 318.2 of the 321.1 relief innings in May through August. They were pretty much the definition of dependability and consistency during this period. However, in September, 31.1 of the 97 bullpen innings were pitched by Taijuan Walker, Lucas Luetge, Erasmo Ramirez, and Carson Smith. I don't mean to suggest that these four gentleman were solely responsible for the decrease in production, (Luetge and Ramirez did give up two home runs a piece, but Smith and Walker performed admirably); however, the "routine" and the "roles" of the men in a bullpen are often anecdotally referred to as being important to their success. This disruption to their routine could have contributed to an overall decrease in bullpen performance... but this is just speculation.

The Mariners were 4-6 in the games where their bullpen surrendered September home runs. Surprisingly, none of these dingers put the opposition in front. They either cut into a Mariners lead or made a deficit that much harder to overcome. Fortunately, giving up so many September long balls doesn't appear to have directly cost the Mariners very many wins. The average WPA for those 12 dingers was only -0.044 (compared to a season average of -0.100) and only two of them carried penalties worse than -0.067. The bullpen did fail to "keep Seattle in the game" as consistently as they had earlier in the season, but several of the games where M's relievers gave up home runs were already blow outs so it didn't really matter. The fact that some of these games weren't close could've also impacted the concentration level of the relievers; it's probably a bit harder to give 110% in the eight inning of a game when your team is down by six runs. I can understand how this might lead to less focused pitches.

It appears that the increase in the HR/9 rate of the Mariners bullpen is probably attributable to a combination of regression, fatigue, and the fact that worse pitchers were pitching (Luetge and Ramirez's 13.2 combined innings of mediocrity). However, although the spike in their HR/9 rate looks ugly on the stat line, most of those home runs were surrendered in blow outs and didn't really cost the Mariners any games.