SAN DIEGO — On one of the first mornings of spring training, Kenley Jansen and Justin Verlander crossed paths in the clubhouse. They stopped for a tight handshake and quick hug.

“I don’t think I’m the oldest anymore,” Jansen told Verlander.

“How old are you?” Verlander said.

Jansen is 38. Verlander turned 43 in February.

“You have five more years!” Verlander said.

Verlander and Jansen are a pair of likely Hall of Fame pitchers who have helped drive up the average age of this otherwise young Detroit Tigers team to 29.5 years, the ninth-highest in the league.

Verlander, though, is the unquestioned elder statesman, an inspirational presence even to someone like Jansen, a closer whose 477 saves trail only Mariano Rivera, Trevor Hoffman and Lee Smith in MLB history.

“It tells you that I can keep going, too, if I wanted to,” Jansen said. “Watching him, seeing how long he’s doing it, why not?”

Verlander, who played the first decade-plus of his career in Detroit before spending time with the Houston Astros, New York Mets and San Francisco Giants, will make the first real start of his long-awaited return to the Tigers against the Arizona Diamondbacks on Monday. Finally, the reunion will come to more vivid life, with eyes glued to television sets across Michigan as the three-time Cy Young Award winner pitches in Phoenix.

Verlander felt twinges of nostalgia all spring: driving familiar roads into the team facility, seeing his own picture on the wall, walking past a photograph of Al Kaline, hearing the Lakeland, Fla., crowd roar once again. The Tigers are three games into the season, and Verlander has already used the term “full circle” to the point of exhaustion.

But what does full circle actually look like? And how is a living legend meshing with a youthful clubhouse?

Watching Verlander and talking with his teammates, a couple of things have stood out. The first is intrinsic: the determination that still pours from Verlander.

“I’m probably going to say what you heard from a lot of the guys,” right-hander Casey Mize said. “I think we’re surprised at how he’s continuing to try to get better. It’s constant — I don’t want to say ‘tinkering,’ because that seems like he’s searching for something. But he’s trying to get better, when he could just come in and say, ‘Hey, this is what I’ve done, and this is what I do.’ We could all say, ‘Yeah, we know, do your thing.’ But it’s a constant drive for more.”

Verlander has asked other pitchers about their arsenals and sought feedback after nearly every pitch in bullpens. It is that sort of commitment and curiosity that has not only fueled Verlander’s Hall of Fame career but also kept him pitching for more than two decades. He is the oldest player in the major leagues.

“Is it in all of pro sports?” Verlander said. “I think it might be in all of pro sports.”

Indeed, LeBron James is 41. Alex Ovechkin and a couple of others in the NHL are 40. Aaron Rodgers played last season at 41. Assuming Philip Rivers, 44, is done for good, Verlander holds the title of the oldest athlete in major North American team sports.

That leads us to another thing that has surprised the younger Tigers about Verlander.

The man drinks a lot of coffee.

“Yeah,” Mize said, “he’s always got a coffee in his hand. I guess these late nights are getting to him at age 43.”

An image of Detroit Tigers pitcher Justin Verlander at the end of his pitching motion, after releasing the baseball.

Detroit Tigers pitcher Justin Verlander throws a bullpen session during spring training. (Junfu Han / USA Today Network via Imagn Images)

In spring training, Mize and Tigers ace Tarik Skubal honed their barista skills with an espresso machine Mize purchased. Skubal recently bought an even nicer machine for the team’s clubhouse in Detroit. It will be stationed between Skubal’s and Verlander’s lockers. Skubal said he has never seen anyone drink as much coffee as Verlander.

“There’s something to that,” Skubal said. “I was around (Clayton Kershaw). He drinks a lot of coffee, too.”

Verlander readily admits that he drinks more coffee than he used to.

“Although I’ve toned it down at game time, so I can get to bed,” he said. “I need my sleep at my age.”

The jokes come with the territory, and Verlander’s willingness to laugh at himself has helped settle any questions about how he would mesh with the Tigers’ young core.

On the field, Verlander begins his Detroit comeback tour with 266 wins, 34 shy of becoming the 25th player in MLB history to reach 300. It could take at least three more seasons to reach the milestone. There is much still to play for.

“This guy had told me since the day I met him, he wants to pitch into his mid-40s,” Tigers manager A.J. Hinch said. “We’re approaching that, and it doesn’t seem like he’s slowing down much. If he has something on his mind that he wants to accomplish, he’s going to put in the work and be really good at it.”

Tigers teammates have marveled at more than Verlander’s resume and presence. He has accompanied rotation mates to watch other starters complete their bullpens. He has already followed through on his promise to learn from them as much as they might learn from him.

“I’ve pretty much adopted Skubal’s entire program,” Verlander said. “I’m just trying to be like him. I’ll let you guys know in a few weeks how that goes.”

In classic Verlander fashion, he wasn’t quite willing to share what he likes about Skubal’s routine or why it might work for him.

“I can’t tell you all the secrets,” he said.

That Verlander’s tenacity and curiosity have already made such an impression shouldn’t come as a surprise. That mindset is central to Verlander’s goal of making this season more than an empty homecoming or swan song. He was less than stellar this spring, posting a 6.75 ERA and surrendering seven home runs in 14 2/3 innings. Verlander and the Tigers hope the regular season and the adrenaline it produces will bring out his best.

“I just want to be successful,” Verlander said. “I wouldn’t be here any longer if it was just like, ‘All right, you don’t have to do that anymore.’ It’s just how I am, and I kind of scratch and claw for any little thing I think can make me better. … I told A.J., and I told Scott (Harris) this: I don’t want a handout here. I’m not just trying to ride off into the sunset and not be successful. I think I still have it. I think I showed that in the second half of last year, and I want to continue to build on that.”

And speaking of full circle: Once traded as part of a deal that sent Verlander from the Tigers to the Astros, catcher Jake Rogers is now working with Verlander and talking to him behind the scenes, another player drawn to Verlander’s experience.

“It’s incredible, man,” Rogers said. “He’s an incredible human. … He’s so knowledgeable about everything. He sees little things that not many people really do. It’s been incredible to talk to him about that and just how he came up, pitch-calling, seeing this, seeing that. There’s a reason he’s been around so long.”