Over the last few weeks, Evan Longoria has been on a tear. He's hit 10 home runs and posted a .324 Isolated Power during August, bringing his season total up to 24 -- that's two more than last season, despite the fact that Longoria only has 447 plate appearances. For all the talk and worry early this season about Longoria not being a power hitter, he's on pace to finish the year with around 30 home runs despite missing a month due to injury. Not too shabby, eh?
But here's a question for you: has Longoria's power been better or worse this season? Even though his home run total is up, that's a difficult question to answer; it depends what statistic you look at. If you just look at his Slugging Percentage (.481), you'd think his power has been down this year, but that's been depressed by his low .236 batting average. And if you look at Longoria's Isolated Power (.244) -- which measures his average extra bases per at bat -- it instead looks like he's improved from last season and been nearly as good a power hitter as he was in 2009.
So what's the correct answer? Well, I don't like Slugging Percentage or Isolated Power as analytic tool; they're good shorthands, but they both have their weaknesses as statistics. So let's delve into Longo's power numbers a bit more in depth.
If you take a harder look at Longoria's power numbers, you see that while his home run total has increased, his doubles have dropped off by a large amount. He hit 44 and 46 doubles the last two seasons -- an average of around one double every 12-13 at bats -- and this season he's only hit 20 so far -- one every 19 at bats. So if we look at his total extra base hit numbers, we get something like this:
Longoria's hitting a high percentage of extra base hits this season, but then again, that's also partly because he's not getting as many total hits this season (remember that low batting average). He's actually hitting an extra base hit less frequently than he has over the previous couple of seasons, and like I mentioned above, he's hitting doubles at a much slower rate than before.
But is this necessarily a problem? Home runs are more valuable than doubles, so if Longoria is trading homers for doubles, then it's possible he's still generating more offensive value this way.
To measure the value Longoria is generating from his power, I decided to try something new: take the current wOBA coefficients and apply them to just extra base hits. This way, I could get the total value created by those extra base hits, and see if Longoria's increase in homers compensates for the drop in doubles. Let's call this total value wXB:
wXB = (1.268 * 2B) + (1.61 * 3B) + (2.086 * HR)
As it turns out, Longoria is providing more value with his power this season than he did last year -- look at the normalized wXB/AB column -- but it's still not as much as he did in 2008 or 2009. Of course, one can argue that Longoria's early season foot injury sapped him of his power and his recent production is more what we should expect from him going forward. His recent homer surge has been an encouraging sign, so if that injury did slow him down in the beginning of the year, next season could be a very exciting one.
Keep hitting those home runs, Longo. But if you could add in some more doubles as well, that'd be really awesome.