GLENDALE, Ariz. — Nothing drives home the fleeting nature of athletic greatness quite like the ace pitcher entering the autumn of his career. Clayton Kershaw turns 31 on Tuesday, a year older than Sandy Koufax was when he threw his final big league pitch, the same age Pedro Martinez was when he had his last transcendent season. There are a finite number of untouchable pitches in a great pitcher’s arm, and no one knows precisely the number left in Kershaw’s.

Here in the waning days of spring training, ahead of his 12th season in the majors, Kershaw and the Los Angeles Dodgers are facing two big questions about the future, one of them short term and relatively benign, the other long term and loaded with big-picture implications for both athlete and team.

The short-term question: When will Kershaw be ready to pitch in 2019? A sore shoulder in camp has left him behind the Dodgers’ other pitchers, and he has been limited to a handful of mound sessions but no game action this spring. It has been nine years (2010, Vicente Padilla) since anyone other than Kershaw started on Opening Day for the Dodgers, but on Monday, Manager Dave Roberts announced what had seemed like a near certainty — Kershaw will not be ready for their March 28 opener.

But it is the long-term question that hovers most profoundly over the 2019 Dodgers as they attempt to get back to the World Series for the third year in a row and this time bring home the title: What sort of pitcher will Kershaw be for them going forward? And a corollary: Can he ever get back to being the brilliant and dominant Kershaw of old?

“I think there’s still a dominant version of Kershaw,” said Andrew Friedman, the Dodgers’ president of baseball operations, whose own future, to some extent, depends on that of his ace left-hander, “that I suspect we’ll see for years to come.”

The run Kershaw enjoyed from roughly 2011 to 2017 was in the neighborhood of peak Koufax, peak Martinez or peak Greg Maddux, which is to say it was among the greatest sustained runs of pitching in modern baseball history. It included three Cy Young awards (and two runner-up finishes) and an MVP, plus four ERA titles and three strikeout titles. His career ERA of 2.39 remains the best of any starting pitcher since 1930, and his ERA+ (adjusted for ballpark and league) of 159 is the best in history.

He learned to adapt as time and back injuries robbed his fastball of a couple of ticks, from an average of 94.4 mph when he broke into the majors in 2008 to 92.8 mph in 2017, a year in which, at age 29, he went 18-4 with a 2.31 ERA and finished runner-up to Max Scherzer for the National League Cy Young.

But after averaging 215 innings across his first seven full big league seasons, he has averaged just 162 over the past three. In 2018, he managed to post a solid 2.73 ERA between a pair of trips to the injured list. But his average fastball velocity was down to a career-low 90.9 mph, and the lingering image of him was his walking off the mound at Dodger Stadium as the losing pitcher in the decisive Game 5 of the World Series, in which the Boston Red Sox tagged him for three home runs.

At that point, no one knew for certain whether they had seen the last of Kershaw in a Dodgers uniform because of the player opt-out in his contract. Ultimately, he exercised the opt-out but re-signed with the team in early November on a three-year, $93 million extension that keeps him with the team through 2021.

“It gives me a chance to prove a lot of people wrong,” Kershaw told reporters after signing the extension. “I think [in 2018] — maybe rightfully so — there’s been a lot of people saying I’m in decline or I’m not going to be as good as I once was. I’m looking forward to proving a lot of people wrong with that.”

Soon thereafter, Kershaw launched an offseason training regimen, overseen by Dodgers strength and conditioning coach Brandon McDaniel, designed to restore the explosiveness to his delivery and thus regain the lost power to his fastball.

“Even at the end of last year, he was talking about the [training] program he was going to do in the offseason — all the work he was going to do to get back to where he wanted to be,” Dodgers pitcher Ross Stripling said. “He’s a guy with a ton of pride in what he does. He could have — I don’t want to say coasted — but he could have gone out there with what he had last year and still gotten guys out. But that wasn’t good enough for him.”

It is easy to speculate now, in hindsight, that Kershaw overdid it this winter — that in an effort to regain his lost velocity and return to his dominant form, he pushed his body beyond its limitations at this point in his career. But Kershaw, who has been keeping a low profile with the media this spring, was not made available for this story, and Dodgers officials were hesitant to draw a line between Kershaw’s rigorous offseason program and his shoulder problems this spring.

“With Kersh, you can always say he overdid things, every day of every week and every month,” Friedman said. “He likes to work. He didn’t feel great about his delivery, his execution. He always likes to do more. I think part of what makes him the greatest pitcher since I’ve been alive is his desire to be the greatest pitcher in generations. He’s motivated by greatness. It’s not just something he desires. It’s something he works as hard at as anyone I’ve ever been around.”

The Dodgers, whose roster depth consistently rates among the best in the game, are well set up to deal with whatever version of Kershaw shows up in 2019. In 24-year-old right-hander Walker Buehler, they have a young pitcher on the verge of ace-hood himself — and a potential fill-in for the Opening Day assignment. In lefties Rich Hill and Hyun-Jin Ryu and right-hander Kenta Maeda, they have veterans to fill in the rotation. And in Stripling and Julio Urias, they have adequate depth to cover for any absences.

But the Dodgers are at their best when Kershaw is at his, and it remains to be seen whether the latter is possible anymore. In 2018, for example, opposing batters slugged .518 against his fastball — up nearly 200 points from his 2009 peak (.319), according to data at At the same time, the small difference in velocity between his fastball (90.9 mph) and his slider (88.2) reduced the effectiveness of the latter. Part of Kershaw’s new reality could involve finding a different mix of pitches to attack hitters.

“With a lot of great pitchers, we’ve seen changes in repertoire as they get into their 30s, and it’s just a natural evolution that I think we’ll see with Kersh,” Friedman said. “I don’t think there’s any great pitcher who did it exactly the same way in their 30s as they did in their 20s.

“And with how strongly he desires to be great, I would bet on him being on the front end of figuring that stuff out before the hitters tell him he needs to.”

Read more: