Over and Undervalued Power Hitters

Earlier this week, I spent some time explaining an alternative way of evaluating power: Weighted Extra Bases (wXB). It’s not a statistic you’ll find in the FanGraphs pages as I made it up — although I am not the first to do so — but I like to think it does a better job at capturing the value a player creates through power than Isolated Power or Slugging Percentage.

That’s not to say that wXB is better than ISO or SLG — simply that it’s answering a different question. While ISO and SLG concern themselves with a player’s extra bases and total bases, wXB focuses specifically on the value a player adds through their extra base hits. The formula uses the coefficients for each hit from wOBA, so doubles are given slightly more weight than in ISO, and home runs slightly less.

Using this stat, we’re able to see which players are over- or undervalued by ISO, compared with how much value they have actually contributed through their extra base hits. There are a few notable names on both sides of the coin, so let’s check them out.


In order to determine which players were over- and under-ranked, I calculated out the wXB ratings for all qualified hitters this season. I then ranked them based on their wXB score, and compared this ranking to where they fell when sorted by ISO. So here, I’m highlighting the top five players that were ranked higher when sorted by ISO than when sorted by wXB:

*Note: For the sake of simplicity, I’m presenting wXB in a form that looks close to ISO. This was called wXB/AB in my previous post, and it’s on a slightly lower scale than ISO.

It should be obvious, but all of these hitters are ones that have a large amount of home runs but few doubles or triples this season. Brian McCann and Corey Hart are especially interesting, as they both have Slugging Percentages above .500, putting them both around the top 30 in the league when ranked by Slugging. But when ranked based on the value of their extra base hits, both these players end up around 50th best.

Another interesting case here is Dan Uggla. Uggla has slugged over 30 home runs, yet his Slugging Percentage is a mere .453. Since 1990, there has only been one player to hit 30 home runs or more and finish with a lower Slugging than Uggla: Mark Reynolds in 2010 (.433). Uggla is currently tied for second place with Troy Glaus (2002) and Curtis Granderson (2009), so if his Slugging dips any lower this season, second place will be his alone.

Another fun note: Dave Kingman was the (excuse the pun) “king” of hitting lots of home runs and little else. In 1982 he led the league with 37 home runs, yet posted a .432 Slugging because he only had nine doubles and a .204 average. Home runs are great and all, but they alone don’t make a complete power hitter.


This list is a lot more exciting if we make it a Top 10. But so I don’t overwhelm you with data, I’m going to limit the other columns:

I’ve been aboard the “Ben Zobrist is horribly underrated” train for a long time, and I doubt FanGraphs readers need another reminder. But holy cow, Jeff Francoeur has over 40 doubles this season? I honestly had no idea. People love to snark about Francoeur, but he’s actually been a valuable player this season and he’s already surpassed his previous season-high of 59 extra base hits.* If this power flash is for real — he is 27-years-old — then there’s no reason why he can’t continue to be a valuable offensive piece for the Royals.

*The numbers I have above are a few days old. Frankie has 61 extra base hits so far this season.

And yes, I know that Reyes and Fowler aren’t “power hitters”, but they have still contributed a lot to their teams through their extra base hits. It’s way too easy to be blinded by home runs totals, but if that’s all you look at, you’re missing out on plenty of hidden value with these players.

If interested, here’s a full workbook on wXB. Enjoy! 

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Steve is the editor-in-chief of DRaysBay and the keeper of the FanGraphs Library. You can follow him on Twitter at @steveslow.

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Mr wOBAto
Mr wOBAto

The impressive thing about Fowler is that his 31XBH have come in 387 ABs and his .868 OPS since adding a leg kick in July hopefully point to his taking a step forward.