GLENDALE, Ariz. -- Kenley Jansen had his worst season as the Dodgers' closer last year and during the offseason, he did something about it.

Jansen had his delivery analyzed and adjusted by a data-driven assessment outfit, changed his winter throwing program and reported to Spring Training this week with an upbeat outlook made only brighter by the new player who lockers next to him, Mookie Betts, and the new one across the room, David Price.

“I got to accept that I wasn’t at my best, and I’ve got to push through it to become a better pitcher,” said Jansen.

The Dodgers won 106 games in the regular season last year, but lost faith in Jansen when it mattered most. When the Dodgers were eliminated in Game 5 of the National League Division Series by the Nationals, by the time Jansen entered in the 10th inning, Clayton Kershaw and Joe Kelly had already given up crushing home runs in relief.

How important is Jansen’s return to All-Star form for a Dodgers title run?

“It’s vital. It’s vital,” manager Dave Roberts said. “To have a guy at the back end with his pedigree, it’s vital.”

Jansen, 32, said that as soon as the season ended, he took the guidance of his agent and Dodgers strength and conditioning coach Brandon McDaniel and had his delivery analyzed at the acclaimed Driveline Baseball in Washington. The result, Jansen said, is a cutter with the rising life of his best years, and not the one that tailed into swing paths last year.

• Notes: Joc's roller-coaster week; SP updates

“Figured out some stuff. It went well,” said Jansen of his time at Driveline. “Learned to get back to where I used to be. My delivery changed so much, and you don’t even know that until they put all that stuff on your body and you figure out you lose eight percent on the cutter, eight percent on the rising. They give you exercise to put you back in position to fire the ball again.

“It feels like the ball has life on it. That’s what everybody’s telling me. One thing I see: It doesn’t go down, it stays in one lane.”

Roberts said this week that Jansen will be more aggressive in his spring program, which in past years had been dialed back to help recover from long and grueling seasons. Jansen said that means that he never shut it down after the season, so he wouldn’t have to go through the typical build-up phase.

“To stop throwing and start it up again, sometimes you feel all achy,” Jansen said. “This time, I took the approach of continuing to throw so my arm would stay in shape. Personally, I kind of feel better.”

Roberts traces Jansen’s mechanical flaws to the strained left hamstring that Jansen sustained in the spring of 2018.

“As he felt healthy,” said Roberts, “things were compensated and he wasn’t finishing and the ball doesn’t do what it’s supposed to do. Overlaying ’17 with ’18 and ’19, a light bulb went off. He’s where he needs to be. There’s a cutter to a right- or left-handed hitter; now there’s a two-seamer he can run off the barrel off a lefty or in on a righty that he trusts, and a breaking ball with depth he feels he can strike [with] early in the count or [use to] get back into a count.”

Roberts said that he and catcher Will Smith noticed a difference during Jansen’s bullpen session Friday.

Jansen also said he’d prefer to focus on 2020 and a loaded Dodgers roster chasing a championship than the lingering noise of 2017, which he believes set in motion his regression.