Friday, August 19, 2011

Guest Post from Donovan Moore: Is Matt Wieters Tired at the Plate?

Another guest post form Donovan and I thank him. I am also supposed to pass along that the August stats referenced in this post are through August 11th only. Enjoy!

This kind of seems like a funny question… what is being asked? Do we catch glimpses of the young catcher yawning in between pitches? Is he taking afternoon naps in the clubhouse? While those are certainly hilarious images—this is not what I mean.

More and more frequently I have been hearing conjectures and comments about how Matt Wieters’s offensive performance “could” or “would” be “better” if he wasn’t so tired out from catching so many games. On its face, this argument seems like it has the potential to be true. A young guy in only his second full Major League season at the most demanding position on the diamond must need some sort of grace period to get used to the wear and tear that catching puts on his body. The expectations put on Wieters’s expected offensive performance when coming through the ranks in the Minors were so extremely out-of-this-world that for him to have fallen so short of them must demand an explanation of sorts…right?

I decided that it could not hurt to attempt to investigate this subject statistically. To begin, I had to determine which stats I would investigate in order to see if the numbers would lend themselves to the argument that Wieters is in fact tired at the plate. The offensive numbers that I decided to take a look at were batting average (AVG) and slugging percentage (SLG). Batting average is the most basic statistic kept on hitters—what percentage of at bats does this guy get a base knock? However, I needed a statistic to qualify these base knocks--and that’s where SLG comes in. SLG is a measurement of how many total bases a batter gets per plate appearance, on average. The differences between a single, a double, a triple, and a home run are all given equal weight. A guy could have an AVG of .350, but if he only hits singles, it’s highly unlikely that he will be nearly as valuable as a guy who is batting .250, but hits a home run every hit.

When looking at SLG and AVG, it made perfect sense to me that if Wieters was in fact tired, he would get less hits (AVG) and they wouldn’t go as far (SLG). Having established which measures of offensive production will be used is one thing, but how does one measure how tired any given player is on any given day? I devised two ways to attempt to measure Wieters’s level of “tired” in any given game. In order to do this, I categorized every game that Matt has played in the 2011 season as either, “he didn’t have the previous day off,” “he had the previous day off,” or “he had the previous day and at least one more consecutive day before the previous day off”—including the first game of the season and the game immediately following the AS break. I took SLG and AVG numbers that he posted in games when he had the previous day off and compared them to his season base line.

This is what I came up with:

2011 season base line: .256 AVG .391 SLG

2011 “he had the previous day off”: .254 AVG .377 SLG

2011 “he had the previous day+ off”: .277 AVG .556 SLG

The only number among these that look anomalous is the .556 SLG when Matt has had more than one day off in a row. However, the other fishy number that goes along with having more than one day off for Wieters is his BABIP (batting average on balls in play). In these games, Wieters has a .357 BABIP. Given his LD% (line drive rate) in these games, his expected BABIP is .334. The couple of extra hits on these days have simply been a couple of extra line drives falling in for doubles. Wieters’s season LD% is 18.2 (for an expected BABIP of .302). His LD% in these games is 21.4%. He is outperforming his expected BABIP by .023 on during these games. During the season as a whole he is underperforming his expected BABIP of .302 by -0.016 with a .286 mark. Given the fact that these games where he’s been sufficiently rested have only amounted to 14 at bats for Wieters, I am pretty comfortable saying that the spike in SLG is due in part to small sample size, and in part to the fact that his BABIP (largely a “luck” statistic) is just simply higher on these days. Simply stated: Wieters have just been luckier in these 14AB than he has been during the rest of the season.

So, Matt is not performing phenomenally better on days after he has been rested or had a break. The other way to measure whether he is tired at the plate or not is to compare his season statistics per month. If he is tiring out over time, we should see a decline here. This is what I came up with after doing so:

April:  .260AVG /.493 SLG

May:    .278AVG /.344 SLG

June:   .247AVG /.383 SLG

July:   .235AVG /.376 SLG

August: .262AVG /.357 SLG

…or graphically:

Wieters AVG has more or less been stable monthly. The only number that really sticks out here is his .493 SLG in April. One could argue that after slugging the crap out of the ball in the first month of the season, Matt just got tired. However, I feel pretty safe saying that if Wieters truly was tired that the drop off in SLG would be steady instead of being drastic one month and then rebounding slightly again. I’m not comfortable saying that one outlier has any statistical significance.

The conjecture that Wieters is tired at the plate makes perfect sense on its face. However the stats just simply do not lend themselves to this argument whatsoever. Who knows whether this level of production will persist throughout his career, or if there is a big break out on the horizon for the Orioles’ young catcher? Either way, if he can maintain his current level of defense, he really doesn’t need to hit very much at all to be a valuable player.

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