From 2008-11, Tim Lincecum and Justin Verlander were two of the five best pitchers in the world. The only three pitchers with a higher Wins Above Replacement total than those two over that time period were into their 30s. Verlander was coming off an American League Cy Young Award victory in '11; Lincecum already had a pair of National League Cy Young Awards under his belt from '08-09. They were both under the age of 28, and they were seen as perhaps the two most likely pitchers of that time to go down as all-time greats.
We know what happened with Lincecum. The following year, he lost his fastball. Without the fastball, he struggled to adapt. Essentially overnight, he became ineffective. Now, five years later, it looks like his career might be over.
Verlander began to lose his fastball in 2013, and by '14, he, too, was beginning to look ineffective. The strikeouts plummeted, and just two years removed from Lincecum's swift decline, we began to question whether Verlander was hurt or if he could ever be a front-line starter again. All signs pointed to no. As recently as midseason '15, Verlander looked like one of the least valuable players in the game. It seemed as if we'd lost another one of the greats to the dreaded fastball decline.
Except, something has happened. Over the past calendar year, here are the five most valuable starting pitchers in baseball, according to FanGraphs' measure of starting pitcher WAR:
    Clayton Kershaw, +8.6 WAR
    Jake Arrieta, +6.7
    Stephen Strasburg, +5.7
    Noah Syndergaard, +5.7
    Verlander, +5.5
Dating back 365 days, Verlander is back to being one of the five most valuable pitchers in the game. We thought these days were over. During the past year, Verlander has made 34 starts and has thrown a league-high 230 2/3 innings. He has always been a workhorse. Now, Verlander is back to being a overpowering workhorse. He's struck out more than a quarter of all the batters he's faced, with his vintage above-average walk rate. The ERA has been 3.20, good for a 76 ERA- that's a tick better than Syndergaard and three ticks better than Chris Sale. The FIP has been 3.38, good for an 80 FIP- that's just one tick behind Corey Kluber and a tick ahead of Max Scherzer.

Almost one year ago, FanGraphs' Jeff Sullivan started noticing some signs that Verlander was beginning to look a bit more like his old self. Now, by almost any measure, Verlander has put himself right back into elite company. It's easy to appreciate the rare pitcher redemption story.
A year ago, Sullivan noted Verlander's comments regarding his state of physical well-being, which indicated he hadn't felt right for a while. He noted that Verlander was smoothing out some mechanical things, and that his follow-through out of the stretch indicated a more powerful pitcher. Definitely, health looks to have played a big role in both Verlander's decline and his resurgence. Health affects mechanics, and he certainly needed time to get those back in order. Now, a year later, I'd like to add a couple more developments to the story.
We can start with the fastball. It was the central focus of Lincecum's decline, and could've been seen among the central areas of Verlander's, too. It was no coincidence that both drop-offs in production coincided with a drop-off in velocity. It almost never is. When Lincecum lost his fastball, the issue became compounded by an inability to change. It was suggested that Lincecum would be better off by working around the edges. What happened was Lincecum continued throwing his diminished fastball in the same spots as before -- namely, over the plate to right-handed batters -- and they teed off. Perhaps there was a lesson to be learned in there for Verlander.

When Verlander began to lose some of his fastball, it took a year or so to adapt. That period coincided with his tough 2014. These past couple years, though, Verlander has made a change with his fastball. He's not doing things the way he used to:
Gif: Justin Verlander Heat Map
You can see the difference in 2015-16 relative to the earlier years. The fastball, now, is being thrown higher than it's ever been, and while that might seem counterintuitive for someone experiencing velocity decline, in Verlander's case, it actually makes perfect sense. Here's why.
Four-seam fastball spin rate, 2016, minimum 500 thrown
We know about the effects of high spin on a fastball. It gives them that "rising" effect, which leads to batters swinging under the ball for whiffs and popups. Those rising pitches work better up in the zone, and so despite Verlander's velocity being down two miles per hour from where he was in his heyday, he's learned to use the strength of the pitch to the best of his ability. Among 165 pitchers with at least 200 four-seams thrown this year, Verlander's ranks in the top 20 of both whiff percentage and popup rate.

There's another development. Verlander has long been known for his fastball, and he's long been known for his curveball. The slider and the changeup were there, but they never demanded the same attention. Well, Verlander has changed the slider, and now it's demanding attention. It's easy enough to see how the pitch has changed:
While the rest of his pitches are getting slower, the slider has gone the other way. Verlander's slider is up nearly two full ticks from last year, and three from 2012. He's throwing it harder than he's thrown it for more than five years -- a time when his fastball was regularly touching 100. And after a career of taking a backseat to the heater and the curve, FanGraphs' PITCH-f/x run values grade it not only as Verlander's best pitch this year, but among the best sliders in baseball.

With added velocity, Verlander has upped the usage of the slider to a career-high rate, at the expense of his changeup. He's using the slider against both righties and lefties, while commanding it masterfully to the glove-side corner of the zone. Against it, batters have a paltry .446 OPS. The slider is now serving as a true plus third pitch for perhaps the first time in Verlander's career.
It's nearly impossible for a player to perform at peak ability while attempting to do so injured. That was Verlander's first hump. He got over the physical stuff, and he smoothed out his mechanics. But from there, he took an extra step. Verlander did what so many aging pitchers struggle to do: he adapted. He realized the strength of his rising four-seamer, and he adjusted accordingly. Verlander tweaked with the slider until he found the version that works best. The curveball didn't need much fixing. Now it's all there, and the revamped arsenal is working in sync with the revamped body. This is what makes it so difficult to write off the greats.
A version of this article first appeared at FanGraphs.com.