little pop of horrors

i have been looking at fangraphs' batted-ball data for the cardinal hitters, and one thing really jumps out: popups. the guys in the middle of the order are all getting under the ball. very quickly, here are the cardinal players' career popup rates --- ie, the percentage of their flyballs that stay on the infield --- vs their popup rates for 2007:

just to clarify here: rolen's ratio of 2.15 to 1 means he's popping it up this year 2.15 times as often as he has over the course of his career. another way of stating it would be to say that his popup rate has increased by 115 percent . . . . . i should also disclaim that "career" is misleading, because fangraphs' batted-ball stats only go back through the 2002 season.

what could explain such dramatic increases? the immediate suspicion would be health: rolen and edmonds are both 30somethings with surgically repaired shoulders, and pujols is less than a year removed from a strained oblique that still may be bothering him a little bit. it's worth noting that david eckstein --- who missed 6 weeks with a strained oblique last year and aggravated the injury at the beginning of spring training, missing about 10 games --- also has caught the popup disease: 23.5 percent of his flyballs are staying on the infield this year, vs a career rate of 12.3 percent.

but not so fast: rolen's shoulder was so badly hurt in 2005 that he was crying out in pain when he swung, yet his popup rate actually went dramatically down that year, to 8.5 percent (the lowest percentage of his career). and last year, coming off surgery, he popped it up at his normal rate (11.9 pct, vs a career mark of 12.0 pct). maybe the shoulder is weakening over time, but can it really be that much weaker than it was in 2005? i dunno if it adds up.

an alternative explanation --- more likely, in my opinion --- is that rolen has been anxious and undisciplined at the plate this year, swinging at pitches he shouldn't. for one thing, his walk rate is appalling --- he's only got 4 unintentional walks all season, or 1 per 22 plate appearances; he's walking half as often his career rate (full career now, not just back to 2002) of one unintentional pass per 10.5 plate appearances. he's seeing only 3.38 pitches per plate appearance this year, as opposed to 4.01 p/pa from 2002 through 2006. furthermore, it's not just rolen's popup rate that's out of whack --- all his batted-ball rates are skewed:

he's not hitting it square --- the results that suggest the best wood on the ball, line drives and outfield flyballs, are both way down. he's popping it up and beating it into the ground. you put these two together --- the lack of walks and the poor ball striking --- and the strong suspicion is that he's expanding his strike zone, chasing stuff he shouldn't. i crunched some numbers real quick-like and found ---- these results are just a bit ragged, but i'll vouch for their general accuracy --- that rolen is indeed swinging at more pitches this year than last:

it's not a huge disparity --- he's swinging 5 percent more often. but that's roughly 1 swing a game --- once a game that he chases a ball outside the zone and screws up an at-bat, or gets himself out on a pitcher's pitch instead of waiting for a mistake. i think 1 ill-advised swing per 20 pitches might very well explain most, if not all, of the anomalies in rolen's batted-ball data this season --- and, by extension, most if not all of the difference between an all-star and a washed-up player.

it's also possible that pitchers are simply attacking rolen more aggressively, pitching him less carefully because they no longer fear him; if he's seeing more pitches over the heart of the plate, that would explain why he's swinging more often. but i think it's a plate-discipline problem. i'm thinking back to his at-bat vs ryan dempster last friday night, which i described here: he chased a slider out of the strike zone on 0-1 --- a pitch that, at best, he would have beat into the ground --- and got himself into an 0-2 hole, which then forced him to defend the plate and chase a high fastball (also out of the zone), which he popped out on. if rolen takes that 0-1 slider and gets even in the count, it's a different at-bat --- maybe a different result. maybe that swing was the proverbial 1 in 20 --- the ill-advised hack that keeps screwing him up.

if it's a matter of plate discipline, rather than health, it can be corrected; let's hope that's the case.

re edmonds, i do think it's the shoulder. it really began bothering him in 2005, and his popup rate that year took a permanent spike. jed almost never popped up before that year --- his popup rates were in the 3 to 4 percent range. if he missed a pitch, he missed by a lot; he swung right through it. but in 2005 his rate jumped to 9.2 percent and was still elevated (compared to his previous standard) last year at 6.2 percent. and this year he's popping up 11+ percent of his flyballs . . . . whether due specifically to the shoulder or more generally to aging, that's a permanent change.

another nail in the old boy's coffin . . . .

Update [2007-5-4 10:39:23 by lboros]: a further thought about rolen, which comes courtesy of ryan van bibber of Cardinals Diaspora. ryan writes: "Have you noticed that he's not hitting lefties at all since the shoulder injury? Since the infamous collision on May 10, 2005, Rolen's .245/.324/.410 versus LHP. Before that, he was .295/.436/.546 versus LHP. That, combined with Edmonds' loss of his ability to hit LHP after the 2005 season, is a big reason the Cards are sunk against even the most mediocre of lefties."

so far this season, rolen is 1 for 13 against lhp . . . .