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What the future holds for Bourn and Pence...peek behind the offensive numbers

Michael Bourn and Hunter Pence are the "veteran" young hitters in the Astros' lineup.  Both players have been the youngest hitters whom the manager has consistently written into his batting order over the last two years.  Also, both players are cost controlled, meaning that they are in the arbitration years of their careers, but both players are also likely to see salary increases over the next couple of years.  Both players' names have come up with increasing frequency when fans and bloggers ponder future Astros' trades.  This is surprising when one considers that their names wouldn't have been discussed as trade bait by most fans three months ago.  In a recent Houston Chronicle fanblog, Chip Bailey started off his column with a comment from a fan who said "I'm about ready to give up on Michael Bourn."  Given Bourn's popularity as a local kid in the major leagues, and Pence's strong fan base among Astros' fans, the fact that  disenchantment has resulted in any fans discussing trades is surprising.

Since fans' recent reactions probably are based on both players' sub-par offensive performance so far, I will take a quick look at that aspect of their performance.  I realize that both players have defensive value--and in Bourn's case, that may be his greatest value--and I'm not short changing that part of their game.  Any examination of their trade value would have to consider the defensive side.  However, for the moment I will examine whether we can or should expect their future offensive  performance to improve substantially over what they've shown so far this season.  Put another way, if we thought that Bourn's and Pence's performance so far this year is indicative of what we can expect from them in the future, maybe trade talk isn't unrealistic.  On the other hand, if Bourn's and Pence's performance is just a temporary blip on the screen, trading either player would be selling "low."  And, while selling low is generally a bad idea, that practice is particularly wrong headed if the players are young and cost controlled.

The primary indicator I will use to examine whether their current offensive performance is only a temporary slump is BABIP or batting average on balls in play. As most of you know, BABIP can provide us information on whether a player has gotten lucky or unlucky in finding holes in the opposing defense or perhaps has made outs due to unusually good defense by the opponent. A lower than expected BABIP often indicates that the player's batting average will revert to expectations in the future, either improving or declining.  The hard part of the comparison, though, is determining what a hitters' expected BABIP should be.  One can look at a player's previous BABIP performance, but for young players like Pence and Bourn, the sample size may not be adequate to make a judgement.

I have used the BABIP predictor initially developed in the forecasting method described in this Hardball Times' articleThis subsequent Hardball Times article provides a spreadsheet with a simple application of the BABIP forecasting model. The forecast primarily relies upon factors like speed, strike outs, and batted ball types. The estimates from this model has been ranked as the best predictor of BABIP.  I pugged inputs for Bourn and Pence into the model and arrived at this result, with the forecasted BABIP termed "x-BABIP."


Michael Bourn .362 (.332)

Hunter Pence .322 (.266)

As shown above, both players' BABIP is much lower than what we expected.  More on this after the jump.

Based on the expected BABIP, Pence should have 14 more hits, and Bourn should have 8 more hits.  That would produce a .304 batting average for Pence and a .292 batting average for Bourn.  Normally you would expect an uptick in the slugging for each player will accompany a higher BABIP.  I have a feeling that fans would have a different feeling about trading Pence and Bourn, if their respective batting averages were .304 and .292, respectively.

I'm not saying that the x-BABIP should be taken as a certainty.  These are estimates, and  the results should be viewed as having some risk of imprecision.  However, the magnitude of the disparity between Bourn's and Pence's x-BABIP and actual BABIP makes me fairly confident that both players are temporarily underperforming in the batter's box.  I think the longer term view for both players is more optimistic than their current performance would indicate.

Another check on our conclusion is to look at some fundamental hittting stats to see if they provide a warning flag that this year's results are caused by a basic change in the player's approach or level of skill.  The strike out to walk ratio is a good summary statistic for that purpose.  Pence's 2.05 K/BB ratio this year is somewhat higher than last year's 1.88 ratio but it is better than his 4 year major league average ratio of 2.56.  Michael Bourn's current 1.88 K/BB ratio is better than last year (2.22) and an improvement over his career average (2.29).  This fundamental peripheral batting statistic tells us that Bourn's approach at the plate actually improved.  Pence's K/BB doesn't come up as red flag either.  Both players have a higher than typical GB/Fly ratio (Bourn at 1.67, vs. career 1.32, and Pence at 1.48 vs. 1.14).  While it is conceivable that this indicates a mechanical glitch in their batting, I wouldn't jump to any conclusions.  While players will have fairly consistent GB/fly ratios over their career, over the course of a season, these ratios can move up and down quite a bit.  In Bourn's case, the high GB/Fly ratio is the likely reason for hitting only one HR, but it doesn't explain his low BABIP.  Pence has 11 HRs so far, and a regression in his GB/Fly over the rest of the season likely means that he will hit a few more than 11 HRs over the rest of the season.

My conclusion: don't think about trading Bourn and Pence based on their current offensive performance.  Most likely their offense to this point in the season isn't indicative of their true offensive skill.  I'm not saying that both players should be viewed as untradeable, but I would be cautious about considering any trades at a time when their offense is at a point which is below their likely future performance.