It would have been perfectly reasonable to assume the Clayton Kershaw of 2017 would never return. He was still at the height of his profession then, right before the indications of a steady decline became so obvious. Then the innings piled up, the back issues persisted and the fastball continued to diminish. When the decade wrapped, the prevailing sentiment was that Kershaw would no longer be great, even though his determination might still allow him to be good. We had seen this too many times to think otherwise.

What we're witnessing now, in the midst of the strangest year imaginable, is the sudden reemergence of a generation's greatest pitcher.

Through his first four starts of this 60-game season, the Los Angeles Dodgers' ace is 3-1 with a 2.25 ERA, 29 strikeouts and four walks in 24 innings. And while it might be easy to shrug that off because his four opponents sit a combined 26 games below .500, the stuff is undeniable. Kershaw's fastball is sitting comfortably between 91 and 93 mph, two to three ticks faster than it was through each of the past two years. His slider and curveball look devastating again.

On Thursday, against an inferior Seattle Mariners opponent, Kershaw breezed through seven innings of one-run ball and recorded all 11 of his strikeouts with his slider and his curveball, two breaking pitches he commanded with near perfection.

"That," center fielder Cody Bellinger said after L.A.'s 6-1 win, "was vintage Kershaw."

Kershaw, who often struggled to break 90 mph in 2018 and 2019, is averaging 91.8 mph with his fastball this season, his highest since 2017, the last time he finished within the top three in Cy Young voting. The increased velocity has helped maximize the effectiveness of his breaking pitches, which have accounted for 86% of his strikeouts. His 15.6% swing-and-miss rate stands as his highest since 2016.

"I knew it was in there," Kershaw said recently, "and so I think that's what's frustrating is the last couple of years it's been hard to figure out why it hasn't been coming out the way I want it to."

Kershaw, 32, returned to the Dodgers on a three-year, $93 million extension in November 2018, a contract length that seemed reasonable given the red flags. He approached that offseason intent on regaining some of his lost velocity and worked extensively with Dodgers director of player performance Brandon McDaniel, who helped to stabilize and strengthen Kershaw's body.

What followed was a highly successful regular season -- 16 wins, a 3.03 ERA and Cy Young votes in a historically hitter-friendly environment -- but it also featured a fastball that lagged behind and a slider that often seemed indecipherable from it. It caught up to him in Game 5 of the National League Division Series, on back-to-back home runs by Anthony Rendon and Juan Soto, which helped eliminate a Dodgers team that had won 106 games in the regular season.

Kershaw continued to work diligently with the training staff last winter. He also paid a visit to Driveline, the Seattle-based, data-driven baseball laboratory. When the sport shut down for three months because of the coronavirus pandemic, Kershaw continued to throw, placing him well ahead of his teammates when the season resumed in early July. Since then, he has tapped back into the fastball he longed for. A specific reason eludes him.

"I just know that you reach back and the ball comes out a little bit differently," Kershaw said. "I don't know why other than all the different stuff we've tried over the past 10 months or so. But it's a good feeling, no doubt."

Dodgers pitching coach Mark Prior noted how the increased velocity on Kershaw's fastball has also allowed him to unlock a sharper slider, a pitch opponents are slugging only .333 against this year.

"When it's good, it's hard and it's short and it basically just misses barrels," Prior said. "And so I think that's the other component. Now is the velocity the same on his slider even when the [fastball] velocity is down? Sometimes it is. But I don't think the movement, and the sharpness of the bite, is the same. That's kind of the added benefit. Yes, [the increased velocity] gives him some [margin for error] on his fastball. But I think the arm speed also helps him lock in his really good slider."

Kershaw didn't make his 2020 debut until Aug. 2 because of a back injury that scratched him from his Opening Day start but didn't end up being serious. That afternoon, while throwing 5⅔ scoreless innings against the Arizona Diamondbacks in Phoenix, Kershaw threw a fastball 93.3 mph, a velocity he hadn't reached since April 2018. Two starts later, he threw another one 93.5 mph -- his fastest since 2017.

On Thursday, in an outing that saw him record his 2,487th career strikeout to move past Hall of Famer Don Drysdale to rank second in Dodgers history, Kershaw flummoxed the young Mariners hitters with sharp breaking balls but kept his fastball velocity between 91 and 92 mph. After the win, which pushed his team's record to 19-8, Dodgers manager Dave Roberts was asked if this reminded him of the 2017 version of Kershaw.

"I think as far as where his slider is at the last couple turns; the fastball, certainly," Roberts said. "But actually I think there's a little bit more of a dynamic pitcher, using arm side a little bit more, and the curveball usage is up since '17. It's a more dynamic Clayton."

Roberts credits good health and a synced-up delivery to Kershaw throwing a firmer fastball and a crisper slider. Bellinger pointed to Kershaw's unrivaled discipline and work ethic in stating that he wasn't surprised to see his stuff improve -- but the circumstance is nonetheless rare.

MLB.com recently looked through all the instances since 2008 when a starting pitcher lost fastball velocity four or more years in a row and found only six of them -- most notably, Felix Hernandez, Zack Greinke and Justin Verlander -- who interrupted the trend with a velocity increase. But none have done so as dramatically as Kershaw, who averaged 90.8 mph in 2018 and 90.3 mph in 2019.

It's enough to make us think differently about who Kershaw might be moving forward -- even if his own expectations are unchanged.

"I've always thought I could compete," Kershaw said. "Your stuff sometimes comes and goes, but your ability to compete and your ability to manipulate through games and figure out different ways to get outs -- ultimately that's what wins games. I'm thankful that my stuff has ticked up a little bit this year, and I'm gonna pitch as long as I'm having fun. I'm having a ton of fun, and I don't see that stopping any time soon. But as far as stuff and getting better and things like that, I honestly don't think about it a whole lot other than just seeing the significant difference this year and trying to keep that as long as I can."