Mariano Rivera’s Curious Rates

With the activation today of Brian Bruney from the disabled list and the designation of Jose Veras, I thought it a particularly good time to check in the end of the line of the Yankee’s bullpen, Mariano Rivera.

The first year into his three-year, $45-million contract, signed about two weeks after he turned 38, Mariano Rivera posted his best strikeout rate since his first full season in the bigs in 1996. And his 12.83 strikeouts to each walk absolutely shattered his previous career best of 6.92. On top of all that personally controlled awesomeness, Rivera also benefited from a .232 BABIP and the lowest hits per batter faced of his career. Add it all up and it is no wonder he posted a 1.40 ERA. His 2.03 FIP showed it was no fluke though.

Move forward to 2009 and how has Rivera done? Well, noticeably worse is easy to see, but there are some frightening numbers beneath the surface. Rivera’s 7.5% swinging strike rate is the lowest on record for him. There has been a sizable dip in the number of pitches thrown within the strike zone and hitters are not chasing these extra balls out of the zone.

Rivera’s ground ball rate is also at its lowest point on record, though that is over a smaller sample than his individual pitch results. It is no surprise then that the home run rate has increased, though the rate by which is has increased is surprising and not likely to continue. Rivera has allowed five home runs already this season through 26.2 innings. The last time he allowed more than five home runs was 1995 when he was a starter.

Interestingly, Rivera’s strikeout and walk rates have not moved much despite the drastic change in his individual pitch outcomes. 32 strikeouts to just two unintentional walks, and no hit batters, gives Rivera an even better ratio than last year. Given his extreme drop in missed bats and overall strikes thrown however, I would not expect that to continue. It will be interesting to see which regression, the strikeout and walk rates or the home run rate, influences Rivera’s final line the most.



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Matthew Carruth is a software engineer who has been fascinated with baseball statistics since age five. When not dissecting baseball, he is watching hockey or playing soccer.


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Josh
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Josh
7 years 2 months ago

Rivera=Gold

Nick
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Nick
7 years 2 months ago

I have thought of two possible reasons for his less than Mariano-like numbers this year.

1. New Yankee Stadium’s penchant for homers, so he adjusts how he pitches
2. He got used to pitching hurt, and when it got fixed he changed something?

Pure speculation, of course.

joser
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joser
7 years 2 months ago

Of his 5 home runs, the first one was at Fenway (4/24) and the second one at Detroit (4/29, his next appearance) so it seems unlikely he was already adjusting his pitching for a stadium that hadn’t hurt him yet (and hadn’t even yet earned its homer-ific reputation). The remaining HRs were at NYS, two on the same terrible night against Tampa (5/7). Since then, he’s only given up one HR (5/20) in a span of 6 weeks and 15 appearances.

It’s hard to say with events that occur as erratically as home runs given up by closers, but it’s possible his HR rate is already regressing (and/or he’s fixed whatever problem he was having early in the season — ie, he now has adjusted how he pitches, and it’s working).

Mark R
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Mark R
7 years 2 months ago

He’s toast. Rivera for Yuni Betancourt, straight up. The M’s will be doing New York a favor.

Rich
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Rich
7 years 2 months ago

The most inexplicable aspect of Rivera’s last two seasons is that he is still very good in save situations but not good at all in tie games.

Jon
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Jon
7 years 2 months ago

Some obnoxious Yankee bloggers have made that point time and time agian. I wonder has anyone done a legitimate analysis to see if his poor performance in tie games is statistically significant?

Rich
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Rich
7 years 2 months ago

The reason for my post is that I would like to see a legitimate analysis from someone at FanGraphs.

I haven’t read the blogs you referenced, but I’m not sure why breaking up the point is obnoxious.

MPC
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MPC
7 years 2 months ago

Rivera in save situations: .523 OPS against, 8.2 K/9, 4.6 K/BB, .38 HR/9
Non save situations: .581 OPS against, 8.6 K/9, 3.39 K/BB, .59 HR/9

In tie games, the OPS goes up to .665 and the K/BB drops to 2.77. BABIP also goes up to .319 (career .268).

joser
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joser
7 years 2 months ago

He didn’t say that bringing up the point is obnoxious. He said some Yankee bloggers are obnoxious. Which is self-evidently true of almost everything related to the Yankees.

Rich
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Rich
7 years 2 months ago

Thanks MPC. I need to check out his LD% in each situation.

joser,

If you’re a Sox fan, are truly unself-conscious.

joser
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joser
7 years 2 months ago

Not everybody who finds all things Yankee obnoxious is a Sox fan. If anything, the last few years, I’ve been finding all things BoSox even more obnoxious than the Yankees. Which is saying something. And something I didn’t think it was possible to say.

Rich
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Rich
7 years 2 months ago

*bringing up*

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