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Darren Oliver -- Drilling Down in the Data

Okay, Darren Oliver apparently is going to be a Ranger in 2010 (and likely 2011).  As I've said before, I don't think this is a real good signing, primarily because I think there are more glaring needs that should be addressed with the limited funds available.

Oliver has pitched out of the bullpen for Anaheim the past three years, and has been relatively consistent, posting ERAs in 2007-2009 of 3.78, 2.88, and 2.81, and FIPs of 3.78, 3.53., and 3.32.  He struck out 8 batters per 9 last year, against 2.71 walks per 9.  The year before it was 6 Ks to 2 BBs, and in 2007 it was 7.13 to 2.22.

Oliver doesn't throw hard anymore...his fastball the past three years, per Fangraphs, is at around 89 mph, and his slider is 78 mph.  Fangraphs appears confused in previous years as to whether he threw a curve or a slider, listing percentages for each but at about the same velocity.  Last year, they just show him throwing a slider, with no curve, and he appears to basically be a two pitch pitcher right now -- 89 mph fastball, 78 mph breaking ball.  Eddie Guardado, as a point of reference, was at 86 mph FB/78 mph breaking ball the past couple of years.

One of the arguments I've made about this signing is that the Rangers don't need another lefty reliever, particularly a middle reliever.  The counter to that has been, well, Oliver has been more effective against righties than lefties, so he shouldn't be thought of the same way as a lefty reliever.

There's some truth to Oliver being more successful against righties the past three years, but it is a weird situation.  Lefties had a better OPS against Oliver in 2007 and 2009, and righties had a better OPS (though only slightly better) in 2008.  However, drilling down the data reveals the splits to be unusual in certain ways.

Last year, for example, in 123 plate appearances against lefties, Oliver struck out 37 batters and walked just 4, a K/BB ratio better than 9.  In 170 plate appearances against righties, Oliver struck out 28 batters and walked 18, a K/BB ratio of around 1.5.  Lefties, however, had a .355 BABIP against Oliver last year, versus a .250 BABIP against righthanders.

In 2008, Oliver had a K/BB ratio of 4.17 against lefties, versus a 2.30 ratio against righthanders, without a huge split in BABIPs.  In 2007, Oliver had a K/BB ratio of around 2.5 against lefties versus a little over 2.0 for righties, but again, with a big BABIP split...a .338 BABIP against lefties, a .247 BABIP against righties.

This large spread in BABIP, along with the fact that Oliver allowed homers at a slightly higher rate against lefties (8 against lefties over the three years, 7 against righties, while facing righties about 40% more often), explains why lefthanders have produced a better slash line against Oliver the past three years.

Now, the relevant question for the Rangers is, is Oliver's success against righties, which is driven by the large BABIP splits, sustainable?  Is this something that is peculiar to Oliver, and inherently generates better splits?  Or is this just an aberration?

I don't know.  I'm not in a position to answer that question.  I can say that, looking at Fangraphs, Oliver's line drive percentage has been well below average the past three years, which suggests that opponent's aren't making good contact against him.  At the same time, though, one would normally believe that if he was truly as successful against righthanders than against lefties, then it would show up in his K and BB rates. 

So I'm not confident that Oliver is someone who is going to have reverse splits...he seems like someone who, most likely, is going to have more success against lefties than against righties in 2010.  Which, if C.J. Wilson and Ben Snyder or Clay Rapada is also out in the pen, means that half your non-closing relievers are guys you'd rather have face lefthanders than righthanders.

Another odd thing in Oliver's splits is his home/road performance over the past few years.  In all three years, Oliver allowed a lower slash line at home than on the road, and in 2007 and 2008, it was a significant difference.

In 2009, Oliver had a better ERA on the road than at home (2.35 v. 3.12).  However, he had a 5.00 K/BB ratio at home, versus 1.79 on the road.  His K/BB ratios weren't as dramatic in the previous two years -- and in 2008, he had a better ratio on the road than at home -- but he did have huge BABIP splits, allowing a BABIP at home in the .220s in 2007 and 2008, and well over .300 on the road in those years.

Another outlier on Oliver's chart is his HR/FB the past three years, Oliver has allowed home runs on around 6.5% of the flyballs he's allowed.  The normal rate is 10%, and there's a school of thought that suggests that that normalizes over time...if we look at Oliver's xFIP, which adjusts FIP to normalize home run rate, Oliver is sitting at around 4.00 the past three years.

For what it is worth, CHONE thinks Oliver has another solid year in him, projecting a 3.48 ERA in 2010 with a 51/21 K/BB ratio in 56 innings.  Bill James projects a 3.92 ERA (and 4.12 FIP). 

So Oliver is someone who looks like he should have success in 2010.  I'm not as convinced as some are that he's going to be equally effective against righties rather than lefties, and I'm afraid not spotting him appropriately in terms of platoon advantages will impact his numbers.  But he's someone who should be able to be a contributor out of the pen next year.