GLENDALE, Ariz. -- Cody Bellinger got pitched to differently and struggled initially. The month of May was coming to an end, the batting average was down in the low .200s and anxiety began to set in. The swing changes became constant and the answers remained elusive. Along the way -- throughout a season that was superior to most but disappointing for himself -- Bellinger realized he spent most of his life hitting without purpose. The "how" came so easily that the "why" never mattered.

This offseason was about changing that.

It was about getting back to the mechanics that made him the National League Rookie of the Year in 2017, but also about understanding the elements that made all of it work so well.

It was about gaining enough self-awareness, and embedding the fundamentals so deep into his own memory, that the inevitable struggles were no longer prolonged.

"It's an old Navy SEAL training technique," Brant Brown, the Los Angeles Dodgers' assistant hitting coach, said before a recent workout. "In times of stress, you don't rise to the occasion -- you revert back to your training."

Bellinger finished the 2018 season with 4.2 Baseball-Reference wins above replacement, a mark that was topped by only 30 position players. He reached base 34 percent of the time, displayed Gold Glove-caliber defense in center field and was among the game's most effective baserunners. But his OPS dropped by 119 points, from .933 in 2017 to .814 in 2018. His slash line against lefties fell from .271/.335/.568 to .226/.305/.376, turning the left-handed-hitting Bellinger into a platoon player for the final two months of the season.

"Going forward," Dodgers manager Dave Roberts said, "Cody's gotta be our guy."

Bellinger will return to an everyday role in 2019, spending most of his time in right field while also filling in at his more natural position of first base.

"That's big," he said, "but I also have to go out there and prove it."

Brown initially pushed Bellinger away when he approached him about improving in 2019. The 2018 season had not yet concluded, and Brown wanted Bellinger to focus on finishing. Bellinger touched base again at the onset of the offseason, then took a month off and got to work in December, alternating his work with Brown in Arizona and new hitting coach Robert Van Scoyoc in Los Angeles.

They uncovered video of Bellinger's plate appearances from the 2016 Arizona Fall League and throughout the 2017 season, then split-screened it with those from 2018 and analyzed the differences. They found that Bellinger was no longer applying enough pressure to the ground. He was standing too tall and straight-legged, making it difficult for him to halt momentum once his swing began. He also wasn't efficient enough getting into his swing path. "Too elbowy," as Brown put it.

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Van Scoyoc and Brown wanted to eliminate wasted movement and make everything about Bellinger's approach feel more natural. They implemented more of a hand movement to help his swing flow more easily through the hitting zone, mimicking the motion Bellinger would make while throwing a baseball. They brought his mechanics closer to what they looked like in 2017, when Bellinger displayed good plate coverage, but also accounted for the muscle he added thereafter.

Now, Bellinger said, "I'm in a really good position to where I can be comfortable with my own swing."

Van Scoyoc and Brown will keep a close eye on Bellinger throughout the spring to make sure his approach doesn't stray. Throughout their training, the two wanted Bellinger to gain full ownership of his mechanics. They carefully explained why the positioning and hand movement would help, progressed through drills to make him feel it, then went back to video to show him how it looked, over and over again.

When Bellinger gained comfort, Brown and Van Scoyoc turned on the high-velocity pitching machine to induce stress.

If the mechanics wavered, they went back to basics.

"You train the movement patterns," Brown said. "Then when you get into the box, you just put it on autopilot."

The lows of 2018 were pronounced -- a .655 OPS in May, a .683 OPS in July, a .385 OPS in October -- and Bellinger hopes to mitigate them.

Early on, he was getting tied up by up-and-in fastballs and kept chasing the sweeping breaking balls away from lefties. His batting average got as low as .225 on June 3, and Bellinger never fully recovered. He said he "got outside my comfort zone," and Roberts noticed it in Bellinger's at-bat quality.

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"Mechanically, he was never in sync," Roberts said. "You start looking at the scoreboard and the average and where you're at, and you start pressing a little bit, and the game speeds up."

By the end of August, Bellinger's OPS against lefties was hovering around .700 and the Dodgers were still fighting for a division title. They acquired the right-handed-hitting David Freese to play first base against lefties, relegating Bellinger to the bench for basically half of what remained in the regular season. Bellinger later sat against Chris Sale and David Price in the first two games of the World Series, then again in Game 5. They all ended in Dodgers losses.

"It obviously sucked because I want to play every day," Bellinger said. "But you kind of understand where they're coming from. I don't believe that it's like that in the future. I think it was just, 'We've got to win now, any way we can.' That's how I took it."

The Dodgers seem to agree. Roberts believes it is "very important" for Bellinger's development that he play every day, but will quickly tell you it's also important for his team. Bellinger is an elite offensive player who can affect games with his speed and his defense on nights when the hits don't fall. He's only 23, but is already among the game's most talented all-around players.

He showed it last year, even amid a season that never felt right.

"It's very, very promising that the end numbers, as people say, were average or above average, and I didn't really feel that well," Bellinger said. "It's going to be really cool this year when I'm feeling good to see what I can do."