FORT MYERS, Fla. — On the one hand, what plagued Craig Kimbrel during his first season in Boston, to this point the worst season in his career, was not difficult to identify.

Kimbrel consolidated more than half the earned runs he allowed into three outings, including one in which he walked four batters before Red Sox Manager John Farrell came to get him.

Craig Kimbrel's first season as Boston's closer was the worst of his career. He struggled again Monday in the 2017 season-opener. Associated Press/Elise Amendola

A LOST YEAR

Boston closer Craig Kimbrel came to the Red Sox with plenty of fanfare, but failed to wow the faithful last season. Among the lowlights:

• Kimbrel’s 3.40 ERA was the worst of his career. It was 2.58 in 2015.

• His 31 saves were his fewest in a full season. He had at least 39 in each of the previous five seasons.

• He had his highest loss total in a season, going 2-6. His previous high in losses was 3 (three times).

• His 30 walks were the second most of his career, after 32 in 2011.

What generally got Kimbrel into trouble last season was an occasional inability to throw strikes.

On the other hand, while it was not difficult to identify the problem as a lack of control, a solution often seemed out of reach.

“That comes with alignment in delivering the ball to home plate,” Farrell said, “That would be a relatively easy fix, and yet in the moment last year there was some tendency to maybe get side-to-side where command was a little elusive for him.”

“Just throw it over the plate,” Kimbrel said. “That’s easier said than done sometimes, but that’s the goal.”

Kimbrel pitched four-plus seasons in Atlanta as one of the best closers the game has ever seen. He’s one of just nine relievers with three sub-2.00 ERA seasons (minimum of 60 appearances), including a 2012 season that ranks as perhaps the greatest relief-pitching season of all-time. His 0.78 Fielding Independent Pitching mark that season is just ahead of the 0.86 that Eric Gagne posted in 2003. He struck out 116 batters in 622/3 innings that season and walked 14.

Kimbrel took a step back in his lone season in San Diego, the team to which the rebuilding Braves traded him to get out from under the onerous Melvin Upton contract. That season saw Kimbrel strike out 87 and walk 22 while compiling a 2.58 ERA – good for most, pedestrian by his standards.

Dave Dombrowski and the Red Sox acquired Kimbrel a year ago for a package of prospects that included outfielder Manuel Margot, now a consensus top-50 prospect who made his big-league debut late last season. But Kimbrel compiled a career-worst 3.40 ERA with 83 strikeouts and 30 walks, the second-highest total of his career. His ERA ranked 69th among major-league relief pitchers with at least 50 appearances. He was charged with a career-high six losses.

Noteworthy meltdowns included a Colby Rasmus home run in Houston in April, four walks against the Yankees in August, a walk-off defeat in Oakland in September after Eduardo Rodriguez nearly threw a no-hitter, and four earned runs at Yankee Stadium in late September that helped cost Boston home field in the ALDS.

“Some high highs and some low lows,” Kimbrel said. “I just hit a stretch where I was having a hard time throwing strikes, and it led to some runs and some losses.”

Boston reinforced its bullpen with the late-season conversion of Joe Kelly and the December trade for Tyler Thornburg, a pair of power arms. But Kimbrel remains the closer, the reliever whose ability or inability to slam the door will set the tone.

To ensure he does that, the Red Sox have stressed the need for Kimbrel to maintain his posture in his delivery. Staying upright allows him to stay on top of the ball with his hand, so that he doesn’t yank it down and in to lefties or let it sail up and over the head of righties.

“His posture might not have allowed him to stay in line,” Farrell said. “There was a little bit of a bend at the waist. He’d dive in with the lead shoulder. As his delivery was unfolding, he’d end up being a little bit side-to-side.”

“It’s about getting on top of the ball and trusting it,” Kimbrel said.

Kimbrel hasn’t given his mechanics too much thought yet. His bullpen session Wednesday was just about building up arm strength.

“There’s still a lot of spring training to work on things,” he said with a confident smile.

If Kimbrel comes out of spring training throwing strikes, nobody will worry about anything else. If lapses in control continue into this season, however, the work he’s doing now might not feel so simple.