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The Best Age 39 or Older Seasons By a Starting Pitcher

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And why Adam Wainwright could be “John Smoltz” good this season but will never be “Randy Johnson” great.

Philadelphia Phillies v St Louis Cardinals Photo by Scott Kane/Getty Images

On Monday night Adam Wainwright threw an absolute gem.

Nine innings. Two earned runs. 8 strikeouts. No walks. He took the loss but pin that blame on an offense stymied by just-a-bit-better stuff from the Phillies’ Zach Wheeler.

The start before that Wainwright was just as good. He was removed after 7 innings having given up 1 run with 1 walk and 10 Ks. The Cards lost that game because Patrick Corbin happened.

Wainwright’s season stats don’t look that spectacular yet. His era is just above 4.00. He has three losses and no wins on the season. The Cardinals batters are giving all their run support to Jack Flaherty. John Gant is getting all the team’s good ERA luck. But underlying those old-school metrics are signs of dominance from the Cardinals’ senior hurler.

Wainwright is striking out 10 batters for every 9 innings he throws. He’s walking less than 2. He doesn’t give up a ton of fly balls, but when he does, they are leaving the ballpark at an unsustainably high rate – 20.8%. I’ve outlined the staff’s increase in HR/FB rates over the last few years in this space, but that’s not a percentage that will hold up if the rest of Wainwright’s performance stays as-is.

As the season progresses, more of those fly balls will find outfielder mitts. His K rate will probably drop a bit but his walk rate might not change. With those sample size issues sorting themselves out, his ERA should wind up closer to his xFIP – expected Fielding Independent Pitching – which sits at 3.15.

If that’s a familiar number, it’s because Waino’s ERA in 2020 was also 3.15.

Basically, excluding some statistical noise, Wainwright has looked really good in this early 2021 season after a really good (if short) 2020.

Let’s have a little fun with those numbers. My consistent readers know how much I love quasi-math. Assume for a moment that what I’m describing remains true. Waino’s HR rates fall more in line with his recent career. His K rates drop a tad but his BB rates hold steady. His ERA/FIP won’t fall to 3.15, but let’s land it somewhere in the 3.50-3.75 range for 200 innings. That’s much better than projections systems predict, but it’s not completely unrealistic.

(It’s still April. Five months of this baseball season exist only in our imaginations. We’re fans. Let’s imagine it with optimism for as long as we can.)

If I guesstify (or, perhaps, quasitate?) his current WAR per IP rate using the parameters I just outlined – his .4 fWAR becomes about .6 fWAR – and then normalize that to 200 innings, Wainwright would land in the 4.0-4.5 fWAR range for the season if he keeps doing what he’s doing.

That would be a phenomenal season for a 39-year-old, wouldn’t it?

That got me wondering just how rare (you can read that “rare” as “completely unrealistic” if you wanna be a poo-poo head) it would be for Wainwright to produce a season like that at that age. Who has the best age-39 season as a starting pitcher since 2000? And where would Waino fall on the list if the scenario I describe plays out? Fangraphs, of course, has the answer.

There have been a surprising number of highly productive seasons by players in their late 30’s and early 40’s over the last twenty-odd years. Most of them, though, were produced by a very small list of names in the mid-2000s, and some of them might have included some *ahem* unnatural enhancements.

Let’s start with baseball’s greatest outlier – Randy Johnson.

In 2004, at the age of 40, Johnson threw 245 innings and produced a 2.60 ERA and 2.30 FIP for a spectacular 9.6 fWAR.

9.6. 9.6!

That performance ranks 10th in the post “dead ball” era and is topped by a 27-year-old Pedro Martinez (11.6) and a bunch of guys who threw between 275-370 innings. WAR is a cumulative stat, so by WAR per IP, Johnson’s age 40 season is about as good a performance as we’ve ever seen.

Johnson was a late bloomer. The 6’10” fireballer was all gangly arms and legs and walks until he hit age 29. I have no idea what clicked for him, but overnight he managed to cut his walk rate in half – from over 6 per – to the mid 3’s. Suddenly all that crazy velocity and movement was in the zone and batters had to swing at it. He was instantly one of the greatest pitchers the world has ever known.

From 1995 to 2002 Johnson won five Cy Youngs and something called the “Pitcher Triple Crown”. He killed birds with his laser-targeting guided missile system of a left arm. He made John Kruk soil his trousers at an All-Star Game. He turned Larry Walker into a switch-hitter.

Let’s get one thing straight. There is no way in Georgia’s blue-green hills that Adam Wainwright comes anywhere close to Randy Johnson’s age 40 season.

Let’s see if we can’t find something a little more doable for Waino.

Roger Clemens produced some amazing seasons with the Astros in ’04 and ’05 at age 41 and 42. He had 6.0 and 5.7 fWAR seasons, with FIPs ranging from 2.87 to 3.11. As a known juicer, let’s just set those aside for now.

Then there is John Smoltz – a player that I think provides an interesting (though admittedly optimistic) match for an age-39 Waino. In ’06 and ’07 Smoltz was 39 and 40 and stayed healthy – making 67 combined starts. He produced back-to-back 5.5 fWAR seasons rooted in remarkably consistent overall performance. Consider these numbers (stat: ’06, ’07).

K/9: 8.19, 8.62
BB/9: 2.13, 2.06
HR/FB: 10.2%, 8.7%
ERA: 3.49, 3.11
FIP: 3.44, 3.21

That’s phenomenal consistency for an older starter. It’s also not that far off from the numbers that Wainwright could put up if he continues to perform as he has. Maybe Waino allows more HRs. Maybe his FIP and ERA are a bit higher. He certainly won’t climb over 200 IPs in a post-COVID season (Smoltz hit 232 in 2006). Still, you don’t have to squint all that much to believe Waino could produce not-quite-Smoltz-like numbers.

That’s pretty much the way their careers have gone.

While I would not argue that Smoltz and Waino are all that similar in terms of pitching repertoire (Smoltz was a higher octane fastball/slider type), the results they’ve produced in their respective careers are surprisingly complementary (career stat: Smoltz, Wainwright).

Career ERA: 3.33, 3.39
Career FIP: 3.24, 3.41
K/9: 7.99, 7.62
BB/9: 2.62, 2.44
Career WAR: 79.5, 41.7
Career WAR/200 IP: 4.58, 3.79

The huge difference in WAR is the kicker. It shows how much production Wainwright has lost by not arriving in the majors as a starter until age 25 and missing a few seasons with serious injuries. Smoltz wasn’t exactly the picture of health throughout his career. He also spent some time as a closer. Still, he has 1200 extremely significant innings over Wainwright. Those extra innings – and a little bit of hardware – are the difference between being a “Hall of Very Good” player (Wainwright) and a “Hall of Fame” player (Smoltz.)

When it comes to aging starters, there’s Johnson. Then a huge gap. Then a known roid user. Then Smoltz.

Beyond those three are several other seasons to note.

Curt Schilling was very good late in his career. At age 39, he produced a 4.6 fWAR season with the Red Sox in 2006 with a 3.59 FIP in 204 innings.

In 2002, 39-year-old David Wells K’ed less than 6 batters per 9, had an ERA of 3.75, and still had 4.5 fWAR.

Chuck Finley, at age 39, produced a 4.4 fWAR with an ERA over 4.00.

Greg Maddux was matching Randy Johnson Cy Young for Cy Young for a time but didn’t quite have the late-career staying power. A 40-year-old Maddux had a 4.3 fWAR with a high-for-him 3.80 FIP.

You can explore the rest of the list here. I’m not seeing a lot of great comps for Waino down the rankings. Wainwright is likely to K more than a lot of the names in the search. He might also allow a higher HR rate. The game has changed rapidly and 20-year-old comps aren’t all that reliable. Pitchers simply aren’t surviving as long as Wainwright anymore. More recent comparables don’t exist in significant quantities.

One point of note is the names throughout this list. Jamie Moyer. David Bell. Andy Pettitte. Mike Mussina. Tom Glavine. Bartolo Colon. If you’re out of high school, you probably recognize most of these guys. They were all good pitchers. Some were very good pitchers. There are no surprises on the list. Essentially, the better a starter is in their 20s and 30s, the more likely they will be able to remain productive at age 39 or 40. Lesser arms don’t get the chance to throw that long. Health sorts out the rest of the names.

That’s the key for Wainwright’s late-career revival. He’s always had Hall of Fame-level talent. Injuries and a relatively late start to his career will keep him out of Cooperstown. But health late in his career has allowed that superior talent to remain viable. He fits nicely with the names above.

So, a 4-4.5 fWAR season for Wainwright at age 39 is (optimistically) possible. It’s been done by comparable arms in not-so-bygone eras. Simply put, as long as he can keep spinning his curveball, throwing strikes, and staying off the IL, he can probably keep pitching well.

We’re not going to see a Randy Johnson-esque season from Adam Wainwright. He could continue to be “not quite John Smoltz”, though. And that would be quite an accomplishment.