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Is 400 innings really a rule of thumb?

First of all, this column unfortunately comes with required reading.  You'll just have to trust me that it's worth your time.  The article is titled "My Right Arm", from author Buzz Bissinger (Friday Night Lights, Three Nights in August), and appeared in the New York Times.  It's a profile of Kerry Wood, and it tells a story that's familiar to many baseball fans: Wood breaks on the scene at a young age, turns in perhaps the best nine-inning start of all time, then throws an average of 2,845 pitches per start under Jim Riggleman and Dusty Baker and breaks down completely.

(NOTE: you may need to register to read the article.  Which is unfortunate, but also what BugMeNot was invented for.)

While the profile is a great read, what I found perhaps most interesting was a suggested "rule of thumb" that I hadn't heard of before: a pitcher should get 400 innings of work in the minors before being called up.  The theory - espoused in the article by Fergie Jenkins and Nolan Ryan, among others - is that young pitchers need to learn how to get through the game without fatiguing themselves, because it's pitching with arm fatigue - not just pitching, in and of itself - that leads to arm injuries.

Bissinger gives us a couple of examples, on both sides of the rule.  First, the positives:

  • Greg Maddux threw 491.1 innings in the minors, and has been on the disabled list only once in 18 seasons, and has thrown more innings than all but 20 other pitchers in baseball history.
  • Tom Glavine threw 536.2 minor-league innings, and has been in the league 21 years.
  • Curt Schilling apprenticed for 701.2 innings, and is up to 20 years.
  • Randy Johnson has also been in the league 20 years, and threw 418.1 innings before his first here-to-stay season.
And the negatives:
  • Wood threw 281.1 minor-league innings.
  • Felix Hernandez threw 275.1 minor-league innings, and now is hurt.
  • Mark Prior, who is on the disabled list pre-emptively even when he is not injured, threw 189 college and minor-league innings before being called up.
  • Yankees phenom Phil Hughes pitched 237.1 innings in the minors, before getting hurt 10.7 innings into his major-league career.
Interestingly, Bissinger also provides Francisco Liriano as a negative example, despite the fact that Liriano threw 484.1 minor-league innings before his 2006 coming-out party and subsequent arm injury.

With this in mind, I thought it might be instructive to take a look at a few Twins, including those from the recent past and future, to see where we're at with the this supposed rule of thumb.

Johan Santana
Minor-league innings: 382.2 - plus, if you like, 129.2 innings in 2000 and 2001 before Santana was an established major-leaguer
Outcome: He's made 33 or 34 starts in each of the last three years, and has thrown at least 225 innings in each.

Brad Radke
Minor-league innings: 569.2, not counting a rehab stint in 2002.
Outcome: Radke pitched 12 seasons and made trips to the disabled list in 2001 (injured thumb), 2002 (when he hurt his groin a couple of times) and then when his arm fell off in 2006.  But he threw 200+ innings and made 30+ starts in nine of those twelve years (the three exceptions being his rookie year and '02 and '06).  No arm problems, up until everything went wrong at once in 2006.  

Ramon Ortiz
Minor-league innings: 666 - spooky, huh?
Outcome: Only one trip to the disabled list, and that was for a strained groin in 2005.  Started at least 30 games in each season when he was a starter for the whole year.

Sidney Ponson
Minor-league innings: 341.1 (not counting a 2001 rehab stint).
Outcome: Shoulder problems in 2002 kept him out nearly a month.  Also got hurt in several other ways (calf strain, alcohol rehab, etc.)

Joe Mays
Minor-league innings: 439 before making 20 starts in 1999.
Outcome: Arm problems galore.  Missed much of 2002 with elbow problems and eventually had Tommy John surgery.

Kevin Tapani
Minor-league innings: 465.1
Outcome: Pitched thirteen seasons; got hurt a couple of times (in 1990 and again in 1999 and 2000).

Jack Morris
Minor-league innings: 213
Outcome: 18 seasons, 3,800+ innings, made 30+ starts eleven times

Jim Kaat
Minor-league innings: 476
Outcome: 25 seasons, 4,500 innings, 39.5 Gold Gloves

Bert Blyleven
Minor-league innings: Not counting a late-career rehab stint, 123
Outcome: Pitched 22 seasons and nearly 5,000 innnings, leading the league in innings pitched twice and finishing in the top ten a total of nine other times

Nolan Ryan (Note: technically not a Twin, but relevant since he was quoted in the article)
Minor-league innings: 287
Outcome: Pitched for eighteen decades, and got in a million and a half innings

Glen Perkins
Minor-league innings: 283, plus 216.2 at Minnesota in college
Outcome: Arm problems, currently on the disabled list.

So what does this prove? Nothing.  Absolutely nothing.  There's really no correlation between pitching more than 400 minor-league innings, and having a long and injury-free career.  Joe Mays' 439 innings, and Glen Perkins' 500, prove that immediately.  So do Nolan Ryan's 287 minor-league innings and Bert's 123.  There appears to be no relationship, at least anecdotally, between Bissinger's supposed "rule of thumb" and the avoidance of arm problems at the major-league level.

The flaw in Bissinger's logic is that it supposes the following:

  1. Pitchers that throw 400 or more minor-league innings have fewer arm problems in the majors.
  2. Pitchers that have fewer arm problems in the majors have longer careers.
  3. Ergo, pitchers that throw 400 or more minor-league innings have longer careers.
The problem: #2 is certainly true.  But #1, while making logical sense, has no evidence to back it up, and so there's no evidence to support #3.  Though I don't have statistical data to back all of this up, I think we'd have to say that pitchers that avoid arm injuries do it for other reasons, not because they've thrown plenty of minor-league innings.

Bissinger spends much of the article also talking about pitch counts, the real culprit in the careers of Wood and Prior.  But he suggests that the fact that both were kept on low pitch counts in the minors was a hindrance, not a help, when it came to throwing a lot of pitches in the majors.  (Which disproves his own assertion that 400 minor-league innings are important, as he seems to suggest that no amount of minor-league innings would be enough to prepare someone for extremely long starts in the majors, if the pitch counts were kept low in the minors.)

The conclusion: 400 innings is not a rule of thumb.  And Bissinger's suggestion otherwise just doesn't have the data - especially in the Twins organization - to back it up.

(All minor-league data from The Baseball Cube)

(Just for reference, here's a look at a few of the Twins Present and Future, who haven't been around long enough to determine durability:

Boof Bonser
Minor-league innings: 885.2

Scott Baker
Minor-league innings: 482, plus 240.2 at Oklahoma State, plus 137 in the majors in 2005 and 2006.  Grand total: 859.2, counting the major-league ones.

Kevin Slowey
Minor-league innings: 275, plus 342 at Winthrop - total 617

Matt Garza
Minor-league innings: 273.1, plus 241.2 at Fresno State and 50 in the major leagues last year for a grand total of 565

So, even if someone else comes out and proves the 400-inning rule, as long as we're counting college innings, everybody on the Twins should be fine.)