Hiroki Kuroda and 39-year-old starters

One of the least divisive and discussed contracts handed out this offseason has to be the one-year, $16 million deal the Yankees gave to Hiroki Kuroda. On one hand, this makes sense; Kuroda was among the best pitchers in the American League in 2013, finishing with a 3.56 FIP and 3.8 WAR in 201.1 innings. Plus, one-year deals come with far less risk attached to them than multi-year contracts.

Yet Kuroda isn’t your typical starting pitcher. He was 38 years old last season and will turn 39 in February, making him the third-oldest starter in the majors after Bartolo Colon and R.A. Dickey. Prior to coming to the US, moreover, Kuroda threw exactly 1700 innings in Japan, which, combined with his totals in America, would give him the second-most among active pitchers at 2,820 innings.

Given his age and the mileage on his arm (not to mention the hitter-friendly ballpark he pitches in), is Kuroda a more risky proposition for the Yankees than he might first appear?

With that question in mind, I decided to examine how other late-30s starting pitchers have fared as they age into their 40s. Using FanGraphs leaderboards, I searched for all 38-year-old pitchers over the past 30 years who have qualified for the ERA title in a single season and compared their performance to Kuroda’s last year.

The results show a large disparity in performance, ranging from Randy Johnson’s ridiculous 8-WAR season at the age of 38 in 2002 to Frank Tanana’s 0.5-WAR year (in which he finished with a 4.90 FIP) back in 1992.

As a whole, this 28-pitcher group averaged 3.3 WAR, a 3.70 ERA, and a 3.87 FIP in 217.8 innings pitched. They didn’t generally strike out a ton of hitters (6.03 K/9), but they often didn’t walk many either (2.75 BB/9). More importantly, though, the list contains a wide variety of pitcher types, from guys like Johnson and Steve Carlton, who could still strike hitters out by the bushel, to others like John Burkett and Doyle Alexander, who survived largely through smoke and mirrors.

Kuroda himself is reminiscent of a few other 38-year-olds who succeeded mainly by limiting the free pass, stranding runners, and picking up a modest amount of whiffs in the process. John Smoltz’s 2005 season with the Braves (3.27 FIP, 75.8% LOB%, 6.62 K/9, 2.08 BB/9) is eerily similar to Kuroda’s 2013 campaign, while Greg Maddux and knuckleballer Tim Wakefield also put up comparable peripherals.

But how did these starters fare as they turned 39 and 40? Can we expect Kuroda to sustain his success or fall off a cliff at some point in the future?

To find out, I used the same guidelines as above to study the performances of 39- and 40-year-old starters dating back to 1983. At age 39, the year in which Kuroda is now entering, major league pitchers hardly see a drop-off in performance from the season prior. On average, they threw 210.1 innings, while striking out 6.2 batters per nine and walking 2.6. These pitchers also combined to post a 3.86 ERA and 3.80 FIP.

Encouragingly for Kuroda, John Smoltz had an even better season at age 39, and other starters (such as Mike Mussina, David Wells, and Steve Carlton) showed a pitcher could still have success this late in their career by relying heavily on pinpoint control.

I found similar results when running this study for 40-year-olds, though the group did experience a noticeable dip in strikeouts to 5.73 per nine innings. However, this group of age-40 pitchers did average 3.4 WAR (or 3.1 if you take out Randy Johnson’s outlier season) and a respectable FIP that fell just below the 4.00 mark at 3.95. John Smoltz was again quite solid, significantly increasing his strikeout rate, while Tom Seaver, Greg Maddux, and Bartolo Colon found success despite pedestrian strikeout numbers.

Of course, this study is partially affected by a sample size bias, as I’m measuring only starters who qualified for the ERA title in each respective season and not the pitchers who failed as they aged and could no longer start in the majors. Nevertheless, Kuroda has shown he is far closer to the former group than the latter, and given the success of John Smoltz and other similar pitchers as they aged, it appears Kuroda won’t suddenly lose his pitching abilities anytime soon.

For me, the biggest takeaway is that pitchers, like Kuroda, who don’t strike tons of batters out, can still pitch effectively into their 40s. As long as Kuroda continues to limit walks and doesn’t see his home-run and left-on-base figures regress significantly, he should still be a dependable performer for the Yankees.

Add in the fact the righthander’s velocity has held steady in recent seasons, and Kuroda appears to be one of the few members in New York’s rotation who isn’t a question mark heading into the 2014 season.

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All statistics courtesy of FanGraphs.

Alex Skillin is a writer and editor at Beyond the Box Score and also works as a Web Editor for SoxProspects.com. He writes, mostly about baseball and basketball, at a few other places across the Internet. You can follow him on Twitter at @AlexSkillin.