Was Joe Mauer Unlucky Last Year?


When Joe Mauer exploded for his 8 WAR season in which he put up a .438 wOBA, I think a lot of people expected that he would at least hold his power somewhat constant and put up maybe not that good of a wOBA, but somewhere close to a .400 mark was within reach. But this past season he came back to Earth a bit, putting up a .373 wOBA and 5.1 WAR. Was luck the cause of this or was Mauer just not very good?

The first way to look at it is the portion of Mauer’s flyballs that went over the fence. Looking at it this way, we can clearly infer that he was lucky in his 2009 season when 20.6% of his flyballs went for homers. Sandwiched around this mark are 6.5% and 6.7%, which was last year’s total.

Another is by looking at his BABIP and linedrive rates, and similarly by using an xBABIP calculator. Using the handy xBABIP calculator at THT, I found that Mauer’s expected BABIP for last year was .328, which is actually lower than his actual BABIP of .348, implying that Mauer actually got lucky last year.

But thanks to a new (well, relatively new) metric we can go one step further and figure out how lucky he was, if at all. This metric is known as wOBAr, which, you can probably guess, is wOBA with regression. Developed by the guys at statcorner, Matthew Carruth and Graham MacAree (who, by the way, runs my favorite soccer blog on the interwebs), wOBAr is wOBA one step further. To quote Carruth:

wOBAr takes a hitter’s batted ball types and uses his own past success rates on each type to generate an expected wOBA line.

This means that rather than looking at BABIP as a whole, wOBA looks at the type of hits that are dropping in (or not dropping in) and compares them to a hitter’s previous success with these types of batted balls and determines much more accurately whether a hitter is lucky. The easy way to do this is to take a player’s wOBAr and subtract his wOBA (or, perhaps more accurately, his wOBA*, which is wOBA with a park adjustment). Let’s illustrate by looking at Mauer:

2010 wOBAr = .389

2010 wOBA* = .382

That wOBA* is less than wOBAr means that Mauer was actually a bit unlucky last year given his batting history. To go even further, we can determine just how many runs that bastard luck took away from Mauer last year, and we do it in the same way that we convert wOBA values to runs (dividing wOBA by 1.15, and multiplying it by the number of plate appearances). So we get this:

(.007/1.15)*582=3.54

Therefore, Mauer was 3.54 runs “worse” than he should have been last year.

One final interesting note on Mauer. Here are his wOBA* and wOBAr marks since 2007, with the difference in runs included.

Interestingly, Mauer has gotten “lucky” in the previous three years before 2010. Does this mean that he is a lucky player? Does it mean he has the type of skill set to where wOBAr is less applicable to him? I’m not sure. Either way, we can be certain that he is still a darn good player and regardless of the appearance of him being unlucky last year, I expect him to have yet another fine season in 2011.

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