Donaldson, as you may have heard, will be the Toronto Blue Jays’ new third baseman this season, and he just so happens to be incredibly good at hitting baseballs. Of course, this wasn’t always the case. Much like his new teammates Jose Bautista and Edwin Encarnacion, Donaldson was a talented power hitter struggling to fulfill his potential until everything suddenly clicked. His breakthrough came at the end of 2012 and carried into 2013, when he hit .301/.384/.499 with 24 homers for Oakland and finished fourth in AL MVP voting. He put up another prolific season in 2014, adding improved defence for good measure and pushing his wins above replacement total since the beginning of 2013 to 14.1, the third-highest number in baseball over that span. He might be the best third baseman to ever play in Toronto, and he’s certainly the best position player to change teams this past off-season. But there was a time, not long ago, when the baseball world thought he’d peaked.

Josh Donaldson stands in the batter’s box at the quaint-yet-neglected Florida Auto Exchange Stadium in Dunedin, Fla., taking one of his first hitting sessions of spring. Mike Mordecai, the Blue Jays’ coordinator of instruction and a two-time World Series champion, is throwing, and he doesn’t take it easy, moving the ball around the plate, giving the hitters different locations to key in on. Donaldson talks to himself as he hits, constantly analyzing the swings he takes. “Oh, dang, he got me,” he says after yanking one foul. “I swear, I’m not trying to go oppo,” he adds when he shoots three straight into right field. He goes on like that through the entire session, muttering self-analysis just loud enough to hear, talking to other hitters about technique and what they saw. While some ballplayers loaf through their daily exercises, especially during spring, Donaldson sees every batting-practice session as another opportunity to improve—another chance to make even the most minor adjustment to keep getting better. He’s seen the worst of this game and how it can eat even the best players for lunch. He’s seen rock bottom, and he doesn’t want to go back. “If you’re not getting better, you’re getting worse,” Donaldson says. “There’s no staying on one plane. There’s no hovering. You gotta take every chance you can to get better.”

Donaldson was a normal enough kid growing up, albeit with a bit of a temper, whipping his video-game controller at the TV whenever he lost. He always wanted to be an athlete and started to play every sport as early as he could. Golf at 18 months. Football at eight years old. He looked natural on every playing surface he stepped onto, but it quickly became clear he was born to play baseball. He first held a bat when he was four, smacking balls his uncle served up to the other side of the backyard. Soon they installed an eight-by-eight-foot net to contain Donaldson’s growing power, and he would hit balls off a tee into it all afternoon long. He’d take 300 swings right-handed and 300 left-handed, trying to develop himself into a switch hitter. He’d take 300 ground balls after football games and spend all weekend hitting off a pitching machine. By 14 he was damn good, and he knew it. He played with swagger. He pimped home runs. And he kept a chip on his shoulder, going through life as if the world was out to get him, keeping a very small circle of friends and reacting defensively to any hint of criticism.

He went to Auburn University for three years and started playing catcher because the team needed one, not because he particularly wanted to. He was good—if not great—behind the plate, but he could always hit, which is why the Chicago Cubs drafted him in the first round in 2007. He started climbing through their organization, was traded to Oakland, continued to improve and reached the majors in 2010 as a stubborn 24-year-old, trying a little too hard to prove he belonged. “Guys in the clubhouse really didn’t take to him very well,” says Jake Fox, a journeyman utility player who was on the Athletics when Donaldson was first promoted. “They thought he might have had a bit of a sense of entitlement. They thought he needed to learn his place.” Even when he was helping them win, Donaldson’s personality rubbed people the wrong way and kept him at arm’s length from teammates.

Case in point: Donaldson hit his first major-league home run—at Toronto’s Rogers Centre—during the second game of his career. Blue Jays starter Dana Eveland was trying to protect a one-run lead when he threw a first-pitch fastball that Donaldson sent screaming into the left-field bullpen. Donaldson knew it was gone as soon as it left his bat, and when he returned to the dugout after his trot around the bases, his teammates gave him the silent treatment, a ritual shunning for MLB rookies that was quickly broken up when a teammate lifted Donaldson in the air and the rest of the Athletics rushed over to give him high fives. But in the clubhouse after the game, an Oakland win, things felt different. “Everybody was just kind of ‘OK, whatever,’” Donaldson says. “As a kid, you dream of helping your team win with a home run. And then you come in and there’s no celebration. It’s disappointing.”

This spring, Fox sat across a locker-room laneway from Donaldson in Dunedin, trying to earn a spot on the same Blue Jays team that Donaldson is expected to star on. Reflecting on that first season, Fox couldn’t believe his team treated their rookie that way. “That was a really rough place for him to come into,” Fox says. “He’s got a big heart. He’s a great guy. People just needed to understand who he was.”

Struggling to assimilate in the clubhouse where his teammates were ostracizing him, Donaldson then started to struggle on the field. He was quickly sent back down to the minors, where he’d spend the entire 2011 season trying to figure himself out. In 2012, he bounced between the A’s and triple-A, excelling in the minors but labouring whenever he was bumped up. As a 26-year-old with more than 2,000 minor-league plate appearances and nothing but major-league failure to his name, he felt the game was passing him by. “I was becoming a four-A player,” Donaldson says. “That’s a hard label to shake. And I knew I was capable of doing more than I was.” He’d hit well his entire life, and suddenly it was the hardest thing in the world. He figured that if he didn’t make changes, and quickly, he’d squander what little opportunity he had left. “I was at rock bottom,” Donaldson says. “I was at my lowest point. I needed to take control of what was going on. I wanted to be able to look at myself in the mirror at night and know I gave it everything I could.”

So he went to work. When Donaldson got to spend time in the majors during that 2012 season, he leaned on Athletics outfielder Jonny Gomes as a mentor when it came to fitting in with the team, and got deeply into watching video of himself. In the minors, he’d only ever watched his home runs—partly because minor-league stadiums don’t have great camera angles, partly because he wasn’t particularly into self-evaluation—which looked good, but told him nothing about his swing. Once he really started to analyze the available video, he realized his swing didn’t look nearly as good as he thought it did. “There are times in baseball when you have to trick yourself into thinking you’re better than you are,” Donaldson says. “And then there are times when reality sets in and you realize you don’t look good and there needs to be a change. That’s what happened to me.”

He couldn’t stand his own tape, so he looked up some of the game’s most successful hitters—Jose Bautista, Miguel Cabrera and Allen Craig—to see what they were doing. Their swings were beautiful; they hit for power and for average; they had clear approaches and didn’t settle for anything less than the pitch they wanted to hit. All three had elements to their swings—Bautista’s leg kick, Cabrera’s extension, Craig’s stride—that Donaldson thought he could take and adapt. He incorporated a leg kick, adjusted his swing plane and made mechanical changes to his load process, all in order to allow him to see pitches better and take a more efficient path to the ball. He also stopped swinging at every pitch he thought he could hit. He cut the plate into two halves—inside and outside. He started picking one of those zones and just looked for pitches there.

Another key change was getting out from behind the plate. Donaldson played third base in the Dominican Republic during the winter of 2011–12, but the Athletics still viewed him as a catcher until the first day of full workouts at 2012 spring training, when Oakland’s incumbent third baseman, Scott Sizemore, got hurt while doing drills at third. Donaldson, who was on the field at the time, looked at his manager, Bob Melvin, and sheepishly asked, “Hey, you want me to go over there?” Much to his surprise, Melvin took him up on the offer, and after just one day of camp, Donaldson put his catcher’s gear away for good. Moving to third meant Donaldson had far less responsibility on the defensive side of the ball—no more handling the pitching staff, no more game calling, no more strategy. It allowed him to focus more on his hitting, which began to vastly improve.

The more the video study and research helped his game, the more he wanted to keep doing it. He became obsessed with finding minor efficiencies in his swing and tweaking the most minute mechanics. He worked harder than he ever had before. “In this game, there are two types of players—the players who’ve earned it, and the players who it’s given to,” Fox says. “He’s definitely one who’s earned it.” Donaldson still spends 15–20 minutes after every game looking at video of his performance in the field and at the plate, constantly analyzing what he’s doing and how his swing is evolving. He keeps a notebook that he writes in after every game, jotting down details from each at-bat—what pitches he saw, how he reacted to them, how he felt in the moment and what he was thinking. He lets the notes sit for a few hours, or even overnight, before he revisits them, once he’s calmed down from the rush of competition, and tries to use the information to learn more about himself and improve. He knows he’ll have to keep working like that for the rest of his time in baseball. “With how my career has gone, a lot of people want to say it’s a light switch,” Donaldson says, a wry grin creeping across his face. “If only it was that easy.”