CSS Button No Image Css3Menu.com

Baseball Prospectus home
  
  
Click here to log in Click here for forgotten password Click here to subscribe

Premium and Super Premium Subscribers Get a 20% Discount at MLB.tv!

No Previous Article
<< Previous Column
Premium Article Lies, Damned Lies: PEC... (07/16)
Next Column >>
Premium Article Lies, Damned Lies: Lea... (07/30)
No Next Article

July 24, 2003

Lies, Damned Lies

Hitting the Wall

by Nate Silver

the archives are now free.

All Baseball Prospectus Premium and Fantasy articles more than a year old are now free as a thank you to the entire Internet for making our work possible.

Not a subscriber? Get exclusive content like this delivered hot to your inbox every weekday. Click here for more information on Baseball Prospectus subscriptions or use the buttons to the right to subscribe and get instant access to the best baseball content on the web.

Subscribe for $4.95 per month
Recurring subscription - cancel anytime.


a 33% savings over the monthly price!

Purchase a $39.95 gift subscription
a 33% savings over the monthly price!

Already a subscriber? Click here and use the blue login bar to log in.

OK, so it might not have been the most controversial thing he's said this month--even our intrepid Derek Zumsteg didn't dare sweat out this Dusty Baker gem. But the Cubbie manager also made the claim that older players fare better in the second half. Here, in his own words:

"When I was with the Giants, we were a second-half team because we were a stronger team and in better shape the second half of the season than other teams. A lot of veteran teams tend to be like that. Young teams and players start well, where older players tend to find their swing and keep it together once they find it. [The Cubs are] a veteran team."
Dusty's claim has at least some grounding in his own experience--under his management, the veteran-laden Giants were markedly better in the second half in both 2002 and 2000, and marginally better in 2001. (Over the course of his entire tenure, the record is far more ambiguous: in Dusty's 10 seasons at the helm, the Giants played .535 ball before the first of July, and .546 after it). While the Cubs' second half didn't get off to a great start with the injuries to Corey Patterson and Mark Prior, it'd sure be nice to see them still in the race come September. The acquisitions of Aramis Ramirez and Kenny Lofton have the Wrigley faithful in a frenzy; will Baker prove to be a sage or a charlatan?

Not to ruin the fun or anything, but this is a testable claim. By comparing the first and second half performances of players of various ages, we can see which ones really perform best down the stretch. A few simple rules:

  1. Using all seasons from 1999 through 2001, we'll compare each player's BA, OBP and SLG before July 1* with the same numbers after it. (*As you've no doubt figured out, the All-Star break isn't really in the middle of the season anymore; the July 1 date works better).

  2. We'll tally the results based on a player's age as of July 1 of the season in question.

  3. The results will be weighted based on the minimum number of plate appearances that a player accumulated in a given half of the season.

So, for example, if Rafael Palmeiro hits .295 in 350 plate appearances before the break, and .275 in 300 plate appearances after it, we'll take the difference between the two figures (-.020) and weight it by 300, the lesser of the two PA numbers.

Here's how the figures work out by age group:


                Improvement (Decline) After July 1
Age             n          BA     OBP     SLG     OPS
21              15      +.018   +.021   +.030   +.051
22              41      -.002   +.004   -.008   -.004
23              98      +.007   +.001   +.015   +.016
24              141     -.005   -.009   -.015   -.024
25              167     -.003   +.000   -.011   -.011
26              168     -.003   -.005   -.003   -.008
27              180     +.001   +.001   -.007   -.006
28              181     -.012   -.009   -.018   -.027
29              166     -.006   -.003   -.022   -.025
30              143     -.009   -.010   -.025   -.035
31              141     -.013   -.012   -.030   -.042
32              117     +.001   -.002   -.013   -.015
33              95      -.003   +.001   -.009   -.008
34              94      -.009   -.008   -.022   -.030
35              73      -.001   +.002   -.021   -.019
36              53      +.001   -.002   +.001   -.001
37              29      -.022   -.025   -.050   -.075
38              14      +.001   -.009   -.013   -.022
                                        
Young'uns     (21-24)   +.001   -.002   -.002   -.004
Mid-Career    (25-29)   -.006   -.004   -.015   -.019
Veterans      (30-33)   -.007   -.007   -.021   -.027
Old'uns       (34-38)   -.006   -.006   -.020   -.026

One thing that jumps out immediately is that, at almost every age, the position players decline as a group in the second half. That doesn't necessarily imply that the second half is a panacea for pitchers--while September is a pitchers' month, the warm weather of July and August is favorable to offense. Instead, we're dealing with some selective sampling issues. To the extent that most managers fixate on the current season's stats when deciding who to place in their lineup, they'll be liable to continue playing a guy who outperformed his true level of performance in the first half well into the season--call it Tuffy Rhodes Syndrome (TRS). Conversely, a slow starter will get benched, even if he might not deserve to.

The age effects are what we're most interested in, though, and they provide a pretty clear refutation of Dusty's claim. Hitters between the ages of 21 and 24 exhibited almost no difference in their second half numbers, while mid-career (25-29) hitters lost about 20 points off their OPS, and veteran hitters (30-34) lost closer to 30. For all age groups, batting average and slugging average were relatively more affected than on base percentage, which suggests that those statistics are more susceptible to TRS.

We can take a more thorough look at this pattern by means of a regression analysis. We'll skip the details here--write me if you're interested--except to say that the regression was weighted such that the small sample sizes at each end of the age curve didn't have a disproportionate effect on the results, and that it produced the best fit line in the chart below:

Both age and age2 (age squared) were statistically significant predictors of change in OPS, which is why you get a curved line instead of a straight one. Dusty's claims notwithstanding, the downward trend observed on the left side of the graph shouldn't really be a surprise. All else equal, we expect a hitter to be better at age 24 than at age 23, and so we should also expect him to be better at, say, age 23 and 6 months than he is at 23 and 2 months. There's no reason that age-related improvement and decline need be limited to the off-season; to a lesser extent, it also occurs during the course of the season itself. The "rookie wall" phenomenon that's supposedly so prevalent in basketball--whether it's real or not is a question for John Hollinger--doesn't have any relevance in baseball. Young hitters fare relatively better as the season wears on.

The wrinkle is that the trend appears to reverse itself, if only slightly, after a player passes the age of 32. The "average" 35-year-old suffers a second-half decline, but according to our model, it isn't any more profound than that of the "average" 28-year-old.

The trick is that average 35-year-old and the average 28-year-old aren't created equal. The 35-year-old has been selected out on the basis of his durability; most players need to have tremendous conditioning habits to stay in the league that long, and the same commitment to fitness may help those players to fight off wear-and-tear as the season rolls on. The 35-year-old is also more likely to be playing a less demanding defensive position, and to have received more rest days in the first part of the season, both of which can help to limit a second-half slump.

But what about the most demanding position of all--the guys on the mound? We can run the same analysis for pitchers, based on their opposition batting stats. For good measure, we'll also look at their strikeout rate (measured as K/BFP).


                Improvement (Decline) after July 1
Age             n          BA     OBP     SLG     OPS  K Rate
21              11      +.005   +.035   -.024   +.011   -3.3%
22              36      +.019   +.014   +.036   +.050   -1.3%
23              69      +.004   +.002   +.004   +.006   +0.8%
24              100     +.003   -.002   -.008   -.010   +0.0%
25              101     +.007   +.003   +.011   +.014   -0.1%
26              114     -.001   -.003   -.018   -.021   +0.4%
27              113     +.000   -.006   -.011   -.017   +0.7%
28              111     +.011   +.007   +.017   +.024   -0.2%
29              96      +.001   -.007   +.002   -.005   -0.2%
30              97      -.008   -.009   -.006   -.015   +0.4%
31              88      -.002   -.007   -.007   -.014   +0.1%
32              83      +.007   +.009   +.009   +.018   -0.7%
33              69      -.007   -.007   -.023   -.030   -0.6%
34              50      +.003   +.001   -.001   +.000   +0.0%
35              33      +.002   -.004   -.009   -.013   -1.3%
36              26      +.016   +.019   +.015   +.034   -0.6%
37              23      -.006   -.006   -.022   -.028   -0.3%
38              19      -.009   -.009   -.040   -.049   +0.2%
                                                
Young'uns     (21-24)   +.006   +.004   +.002   +.006   -0.1%
Mid-Career    (25-29)   +.004   -.001   -.000   -.002   +0.2%
Veterans      (30-33)   -.003   -.004   -.006   -.010   -0.1%
Old'uns       (34-38)   +.002   +.001   -.008   -.007   -0.4%
Pitchers don't exhibit the same clear aging patterns that hitters do, and so it shouldn't be surprising that their performance deltas in second half are also less dependent on age. Still, there's some weak evidence that older pitchers fare better as the season wears on. Pitchers between the ages of 30 and 33, for example, saw their opponents' OPS decline by 10 points in the second half, while pitchers between the ages of 21 and 24 saw it rise by 6 points.

The trend isn't statistically significant at any strict degree of confidence, but in the interest of equal time, we'll give the pitchers their graph:

Survivor effects play a role here, too--the pitchers who survive to a ripe old age have demonstrated the ability to withstand a heavy workload, while younger pitchers haven't. By implication, limiting a young pitcher's innings in the first half of the season may help to mitigate the extent of the decline, as well as the risk of injury in the future.

What's interesting is that the improvement that older pitchers experience in the later part of the season doesn't seem to bear any relationship to their strikeout rate--older pitchers are hit slightly less hard by their opponents in the second half, even as their K rate suffers a (modest) decline. Although the trend isn't as profound as I'm making it out to be, the first half of the year can be thought to be a power pitcher's part of the season, while finesse pitchers are at an advantage as the season wears on.

None of this is good news for the Cubs, a team led by veteran hitters and younger pitchers. On the other hand, a squad with the reverse arrangement, like the Twins, might seem to be at something of an advantage as the season draws to a close.

That said, it would be easy to make too much of this. Roughly speaking, a difference of 80 points of OPS is worth about one additional run per game. With 60 games left to play, our numbers imply that a team that consisted entirely of 34-year-old pitchers will improve by about six runs relative to a team that consisted entirely of 24-year-old pitchers. Conversely, a team that consisted entirely of 24-year-old hitters would improve by about 14 runs relative to a team that consisted entirely of 34-year-old hitters.

Real teams, of course, rarely display such extreme demographic patterns, and so the upshot of all of this probably amounts to a game or so at the most. Dusty Baker's suggestion that veteran players fare better in the second half is wrong, but in the grand scheme of things, it doesn't make a heck of a lot of difference either way. The quality of the players on the field--and the quality of the leadership coming from the dugout--are far more important determinants of success whatever the time of year.

Nate Silver is an author of Baseball Prospectus. 
Click here to see Nate's other articles. You can contact Nate by clicking here

0 comments have been left for this article.

No Previous Article
<< Previous Column
Premium Article Lies, Damned Lies: PEC... (07/16)
Next Column >>
Premium Article Lies, Damned Lies: Lea... (07/30)
No Next Article

RECENTLY AT BASEBALL PROSPECTUS
Fantasy Article Fantasy Freestyle: Analyzing the Competitive...
Premium Article Minor League Update: Games of Wednesday, Aug...
Premium Article What You Need to Know: August 28, 2014
Eyewitness Accounts: August 28, 2014
Premium Article Skewed Left: A Three-Hour Tour
Premium Article Moonshot: On Regressing Defense
Prospects Will Break Your Heart: Pain Don't ...

MORE FROM JULY 24, 2003
Breaking Balls: Courtesy Lies
Prospectus Triple Play: Arizona Diamondbacks...
Premium Article Under The Knife: Nevin Returns
Premium Article Prospectus Today: Filtering the Noise

MORE BY NATE SILVER
2003-08-13 - Premium Article Lies, Damned Lies: A Roll of the Dice
2003-08-06 - Premium Article Lies, Damned Lies: Quantum Leap
2003-07-30 - Premium Article Lies, Damned Lies: Leading Off
2003-07-24 - Premium Article Lies, Damned Lies: Hitting the Wall
2003-07-16 - Premium Article Lies, Damned Lies: PECOTA Mid-Season Review
2003-07-09 - Premium Article Lies, Damned Lies: Digging in the Backyard
2003-07-02 - Premium Article Lies, Damned Lies: A Whole Different Ballgam...
More...

MORE LIES, DAMNED LIES
2003-08-13 - Premium Article Lies, Damned Lies: A Roll of the Dice
2003-08-06 - Premium Article Lies, Damned Lies: Quantum Leap
2003-07-30 - Premium Article Lies, Damned Lies: Leading Off
2003-07-24 - Premium Article Lies, Damned Lies: Hitting the Wall
2003-07-16 - Premium Article Lies, Damned Lies: PECOTA Mid-Season Review
2003-07-09 - Premium Article Lies, Damned Lies: Digging in the Backyard
2003-07-02 - Premium Article Lies, Damned Lies: A Whole Different Ballgam...
More...