MESA, Ariz. -- A’s left-hander Sean Manaea usually keys in on one particular pitch during Spring Training. Last year, it was mastering his slider with the help of Hall of Fame lefty Randy Johnson.

But this spring, his focus has shifted a bit away from the mechanical side of pitching.

Entering his sixth Major League season, Manaea is beyond the point of tinkering with his pitches. Instead, the 29-year-old lefty is placing more emphasis on the maintenance his body, both mentally and physically.

“I have the stuff. It’s just going out there and doing it,” Manaea said. “Throwing my stuff and trusting that everything I’ve done is enough, like being able to throw my pitches for strikes. When I do that, I feel like I’m one of the best pitchers in the league. I firmly believe that.”

There were moments to back up Manaea’s claim as one of the game’s best last season, primarily over the final month, when he turned around a rough stretch that included a 9.00 ERA through his first four starts by going 4-1 with a 2.77 ERA over his final seven regular season outings. Looking to translate that success over a full season in 2021, Manaea implemented a workout regimen that mostly featured exercises designed to improve his mobility and durability.

For the first time in his career, Manaea worked out some muscles he never knew existed for five days a week. The benefits of that program have already shown up in his bullpen sessions this spring, as he feels a lot more efficient with his movements prior to delivering a pitch.

“There were specific parts of my body that weren’t up to par with everything else,” Manaea said. “I feel like I’m pretty glute and hamstring dominant. I guess my internal abductors are pretty weak. My internal rotation on some stuff is weak. So I started working with a guy and I told him all those things. I did that five days a week this offseason and I’m feeling great.

“A lot of those exercises I had never done in my life. I feel like it’s helped a lot. I can already tell throwing bullpens just how much better I feel. It’s crazy seeing the progress in such a short amount of time.”

For the mental side of his game, Manaea linked up with longtime friend and college roommate Tyler Pazik, a mental performance coach who runs the Pazik Performance Group in Denver, Colorado. Manaea’s goal is to build up a confidence that matches his stuff on the mound. At times in his career, he said he has allowed certain challenges to deteriorate his conviction, leading to inconsistent performances.

“The biggest thing is believing that I’m nasty. I feel like I am too nice sometimes,” Manaea said. “It’s kind of like I’m too easy going when I need to maybe hype myself up. Those kinds of things are big changes for me. Just believing like I have disgusting stuff and using that. I need to express it out on the mound.”

The work with Pazik has gone so well that Manaea plans to continue utilizing him as a resource throughout the season.

“There’s no reason why I shouldn’t have confidence in myself,” Manaea said. “At times, I’ve struggled with stuff like giving up five runs or going through injuries. Now I don’t care about any of that stuff anymore. I’m here to go out and pitch to help this team win a World Series. Just keep it simple and have that belief.”

Adding to that confidence last year was his ability to adapt to a decreased velocity in his fastball, a pitch that has sat mostly from 89-91 mph over the past two years. What was once a worry has now become a fun challenge for Manaea as he gets more creative in finding ways to put hitters away with more finesse and less flash.

“We always have high expectations for Sean when he’s healthy,” manager Bob Melvin said. “I think the thing I’ve been most impressed by him in his time here is he’s been able to be effective in different ways. When he first got here, he was a velo guy throwing 95 mph and getting a ton of swing and misses up in the zone. And then over time, as happens with starters, the velo ticked down a little bit and you have to find a way to be effective a little differently, and he has.”