Even though Austin Jackson struck out four times last night in the 14-inning marathon of a game, he’s still sporting a better-than-league-average 12% strikeout rate. That’s half of his career rate (24%). We’re only talking about 14 games and 74 plate appearances – which isn’t the largest of sample sizes – but we can believe that some of the strikeout reduction is “real”. Just how much of it is real and how much is random variation at work, though, is the question.
I think pretty much every Tigers fan knows the background on Jackson. He burst onto the scene in 2010 with a nice rookie year that saw him hit .293/.345/.400. He struck out a lot – 25% of his plate appearances – but his high BABIP (.396) allowed him to hide this deficiency. The balls didn’t fall for hits quite so often (.340 BABIP) in his 2011 sophomore campaign (while the strikeouts rose to 27%) and his OBP dipped below .320. Jackson changed his approach at the plate with the help of hitting coach Lloyd McClendon in the offseason prior to 2012 and he went on to have his best season yet. The strikeouts dropped five percentage points down to 22%, he drew more walks, the BABIP went back up, and his on-base percentage jumped to .377. He really was everything a leadoff hitter should be.
And this season the trend has continued. As mentioned in the opening, he Jackson has only been punched out in 12% of his plate appearances. If he can keep that rate below 17% for the year, he’ll become only the fourth player since 1955 to cut down the strikeout rate by 5% or more in two consecutive years.
But will he do that? We can’t know for sure, but we can estimate his new strikeout prevention ability based on the work of others. Russell Carleton (now of Baseball Prospectus) has done some oft-cited work in the past about sample size thresholds and when certain statistics become reliable. FanGraphs has compiled a quick-and-easy page with some of the rules of thumb.
Strikeout rate is one of the stats that becomes reliable relatively quickly. At 150 plate appearances we’ve reached the “break even point” whereby the best statistical estimate of a player’s true talent level would include 50% observed results and 50% of the league average result. Another (probably easier) way to think about it is, for strikeout rate, we always want to add 150 plate appearances of average into the player’s stat line.
There might be three ways to do this for Austin Jackson. If we regressed his 2013 line of 12% (in 74 Pas) with 150 plate appearances of MLB average K-rate (right around 19%), we’d figure his “true” rate to be 17%.
But Austin has never been an MLB average striker outer. Even last year, after reducing his rate by a significant 5%, he was punched out at a higher-than-average rate. One could figure that regressing toward his career average of 24% would be more prudent considering he has over 2,000 plate appearances to his name. If we do that, we would figure his new true strikeout rate to be 20%.
But perhaps it’s unfair to regress all the way to his career rate when he already showed some reduction below that line a season ago. A season of strikeout data is a good indicator of true ability (observed and regressed numbers differ by less than one percentage point), so it could be right to use last season as the regression baseline. It doesn’t end up being all that different from using his career line, but it would put him down to 19% — basically MLB average.
So, while 12% looks great so far, it’s probably unrealistic to see him finishing the year at that level of strikeout avoidance. That being said, it’s likely that he is truly continuing in his ability to cut down the K’s. It would be reasonable, at this point, for us to project him to finish the year with a strikeout rate in the 17%-20% range, with 19%-20% being the more likely portion of the rage in my opinion. This likely wouldn’t qualify him for the 5% reduction in back-to-back years, but it would still represent a significant improvement and further encouragement for his development as a potential star-caliber player.