Today, Monday, Aug. 30, Adam Wainwright celebrates his 40th birthday. He’s the second oldest pitcher currently on a Major League roster, behind only Rich Hill. He shouldn’t be here.

By "here," we don't mean St. Louis, because he probably has a lifetime pass to pitch there as long as he likes. When we say "here," we mean in the midst of one of the finest stretches of his career. We mean that he's going to get some Cy Young consideration. We mean that he is, improbably, pitching like an ace again.

What makes it so stunning is if you remember how his mid-30s had been trending, how thoroughly he'd been written off three years ago. After a spectacular age-32 season in 2014, Wainwright landed on the injured list six times over the next four seasons, missing huge chunks of 2015 and ‘18, and posting an unimpressive 4.81 ERA across healthier seasons in 2016-17. When he decided to return for 2019, it was, at 37 years old, without assurances of a rotation spot.

There was a stretch, for a while there, where if you’d looked ahead to the big four-oh and wondered where he might be, you’d probably have said something like “several years into a very comfortable and well-earned retirement.”

Instead, this has happened:

Age 33-36: 4.54 ERA in 390 1/3 IP
Age 37-39: 3.52 ERA in 407 IP

Or, even better:

Age 38-39: 3.02 ERA in 235 1/3 IP

After shutting out the Pirates for seven innings on Saturday night, he's got a 2.97 ERA in 26 starts. He's now one of just 14 players in the years since integration in 1947 to have an ERA below 3.00 at 39 or older.

But really, this isn't just about "being good while advancing in age," it's just about being good. Combining 2020-'21, he’s got a 3.02 ERA, which is a Top-10 mark; he's thrown the second-most innings, and he's tossed the most complete games.

He is, almost certainly, going to get some Cy Young support for the first time since finishing second seven years ago. In nine second-half starts, he's got a 1.97 ERA. Almost no starter in baseball has been more valuable.

It’s an incredible turnaround from one of the most important pitchers in franchise history, second only to the incomparable Bob Gibson in most ways. Today, years after it seemed like his effective career was all but over, he’s been one of the better starting pitchers in baseball. It’s worth the time to focus on the late-career renaissance by one of the most notable pitchers of the 21st century.

It might look better, of course, simply because the rest of the St. Louis pitching staff does not. Cardinals pitching has posted the second-worst strikeout rate in baseball while allowing the highest walk rate (for good measure, they’ve hit the most batters, too). Every non-Wainwright pitcher combined has offered a 4.27 ERA and 4.44 FIP while wearing the birds on the bat this year. Yet here he is, succeeding where his mates mostly haven’t.

So: Where’s this all coming from? The results have changed, somewhat, because he has. After that multitude of injuries -- five trips to the injured list in 2017-’18 alone -- Wainwright created “a new workout regime, a new diet and new trainers to formulate a plan,” wrote Zach Silver earlier this year. It's worked, seemingly; aside from a contact tracing issue earlier this year, Wainwright has been on the injured list just once in the last three seasons, missing 10 days for a hamstring issue in 2019.

That's a good start, and it reminds us this is not just about 2021. This may have started back in 2018, with his best pitch. Let's get back to the “Uncle Charlie.”

Throw the curveball more

Wainwright doesn't fit neatly into the model of the modern pitcher -- and why would he, as his career pre-dates the pitch-tracking era and most forms of social media -- in the sense that he doesn't throw high, hard, high-spin four-seamers at the top of the zone, hunting for whiffs. That's not his game, and it never has been. But for all the attention he's getting in 2021, it's worth noting that he made one important change at the end of 2018, one you probably didn't notice.

That year, he made four starts, then missed four months rehabbing an elbow injury. When he returned in September, the results may not have looked that impressive -- a 4.84 ERA for a third-place team, with some onlookers wondering why he'd even been allowed back to start in the first place. But if you looked closer, something interesting had happened. He'd thrown 17 consecutive scoreless innings on minor league rehab assignments, for one, but he also posted an excellent 25/4 strikeout/walk in the four late-season starts.

"I've got good stuff. I've had better stuff these last four games than I've had these last two years. I've found the youth," he said that fall.

From 2008 through the early season injury in 2018, Wainwright threw his curveball 25% of the time. When he came back that September, he threw it 39% of the time, which was at the time a new career high for any month in his entire career. He's never really stopped, since, throwing it at least 30% of the time in every single month. That is a reflection of the more modern way of pitching, which is "take your best pitch and throw it a lot," even if it's not a fastball.

That's especially true for those pitches which warrant their own nicknames, really. If you have that kind of pitch ... throw it.

The sinker is more effective

So maybe this all started three years ago. No one was putting him in the Cy conversation when he had a 4.19 ERA in 2019. What's different now?

For that, we turn to his fastball, or “fast” ball, perhaps, because the sinking two-seamer Wainwright has long used as his primary fastball was never that fast in the first place -- 91.7 mph at its peak in 2010, which was of course more than a decade ago -- and as he’s aged, through fits and starts, it’s decreased all the way down to this year’s 89.2 mph. (Which, of the 94 starters to throw at least 750 four-seam or sinking fastballs this year, is 87th.)

That’s a trend, perhaps, that belies this chart, in which we’ve highlighted only his sinker and his curveball, his two primary pitches (combined, he uses them about two-thirds of the time this year) and looked at the performance against each of them over the years, using wOBA.

This right here tells you why the sinker is much of what is driving his 2020-'21 improvement, because the curveball is still good (if inconsistently so, and less so than at his peak), yet while the sinker has slowed in velocity, it’s massively improved over the last two seasons. How?

The actual numbers here (.223 sinker, .242 curveball) are less important than the trends and shapes. While he throws three other pitches -- a four-seamer, a cutter, and a lightly used changeup -- they’ve combined for a decent .335 wOBA, roughly what they always do aside from 2018’s injury-shortened year anyway.

So since the sinker is what’s showing massive improvement, let’s focus on that. It’s been so effective, in fact, that it’s been one of the top 20 pitches in baseball this year. Narrowing it down to sinkers only, Wainwright’s got the second most valuable one of the season.

It’s not getting faster, obviously. It’s not avoiding hard contact better. He’s not really throwing it in the zone more. It’s not really getting more swings-and-misses, not that it was a pitch that ever really did that. (It’s really not that, actually; 138 pitchers have had 100 or more swings on sinkers, and Wainwright’s 8.9 swing-and-miss rate is third-weakest.)

It is -- as his curveball is as well -- getting a ton more called strikes, which helps. It may seem like all of these came on May 23, when Wainwright racked up an incredible 31 called strikes, tied for the most of any pitcher in a game this season. (That game also tied his own pitch-tracking-era Cardinals record for most called strikes, set originally in 2013 and tied in 2020. He owns 12 of the top 15 such games.)

But for the season, Wainwright has received a called strike on 45.4% of the sinkers he’s thrown that weren’t swung at, which is his highest since 2012, and a career high. It is, among all the pitchers with 200 takes on sinkers, the 10th best mark. Just look at some of these and enjoy.

But so far as the sinker goes, split it up into what happens when he throws it hitters don’t make contact (so balls, called strikes, swinging strikes), and when they do make contact (so hits, outs, errors).

When no contact is made on his sinker ... the outcomes are good, better than his average, but not in ways he's never seen before.

When contact is made on his sinker ... the outcomes are insanely great, wildly better than he's ever had, better than any regular NL starter this year.

That's largely a credit to Wainwright, who over the last two years has been throwing it lower than he has since 2013, hitting the edges of the zone better with it than he has since 2013, and tying, within decimal points, his best-ever ground ball rate on it. Combine that with the best-ever called strike rate, and the expected outcomes on the pitch are the best he's ever had in the seven seasons of Statcast tracking. It is, without caveat required, a much improved pitch.

And yet: There's one more thing, too. No sinker in baseball has had a larger gap between expected outcomes and actual outcomes, in that Wainwright's collecting contact that should lead to good production actually finding elite production (a .174 average and a .228 slugging), and that is because ...

He’s getting a ton of help from his friends, finally.

The Cardinals defense has been fantastic, but it wasn’t all that long ago that the opposite was true.

In 2017-'18, the St. Louis defense was rated as the absolute weakest collection in baseball.

From 2019-'21, the St. Louis defense is rated as the absolute best collection in baseball.

There's a lot that's gone into that incredible turnaround, from the arrivals of Paul Goldschmidt and Nolan Arenado, to the ascensions of Harrison Bader and Tyler O'Neill, and a whole lot more than that. Of the regular Cardinal starters this year, only rookie Dylan Carlson rates as a below-average defender.

All of which, you'd think, might benefit a pitcher who pitches to contact, and wouldn't you know it: no pitcher in baseball has been boosted by quality defense behind them as much as Wainwright has (and only three have outperformed their FIP as much). We saw that in action from Bader on Saturday night. We've seen that from St. Louis fielders behind Wainwright all year.

We saw something else on Saturday, too. Here's another one of those called strikes. Look where it crosses the plate. Look at Yadier Molina.

Borderline? Perhaps. It's certainly not a bad call, maybe more one that could have gone either way. Thing is, those calls go Wainwright's way more often than they do for anyone else. So far this year, 106 starting pitchers have had 300 pitches taken on the edges of the zone. Guess who has had the most turned into called strikes?

Highest SP called strike rate, edges of zone, 2021

55.1% -- Wainwright
55.0% -- Kyle Gibson
54.8% -- Sonny Gray
54.8% -- Gerrit Cole

While Molina doesn't rate that well in overall framing metrics anymore, there's a considerable difference for Wainwright when he's throwing to Molina as compared to Andrew Knizner. Score another one for Yadi's Hall of Fame candidacy.

Just after he turned 25 years old, back in 2006, Wainwright was the author of one of the most famous postseason strikeouts ever. He was a rookie reliever sending his team to the World Series by striking out one of the game’s biggest stars. At the time, it was reasonable to think that'd be the high point of his career, a moment that could never be matched.

On his 40th birthday, he’s one of the best pitchers in baseball. Again.