Only in MLB can the terms nut and rat be considered high compliments. Toronto third baseman Josh Donaldson is also a geek, a perfectionist, an ornery s.o.b.—and one of the most complete players in the game

IN 1952, Topps manufactured its first full set of baseball cards. The inaugural edition sold well enough that the company produced a second line, for release at the end of the season. That set bombed. Unopened boxes of unsold cards were held in the Topps warehouse for nearly a decade before being loaded onto a barge and dumped into the Atlantic Ocean, settling to the bottom like sunken treasure.

"This card is part of that set," says Josh Donaldson, tapping on an image of a 1952 Mickey Mantle Topps card on an iPad screen. "Between [the card company] getting rid of them, and kids putting them in bicycle spokes and that kind of thing, there aren't very many left."

At a Toronto coffeehouse around the corner from his apartment, Donaldson has been telling the legend of the lost '52 Mantles, now some of the most valuable cards in the world. The Blue Jays' 29-year-old third baseman, who this season has been the best player on the planet this side of Bryce Harper and set a new all-time record for fan votes when he was elected to the All-Star Game, is obsessed with sports cards and memorabilia. Back home in Mobile, Donaldson has thousands of cards, many kept in a safe, including several vintage Mantles. He recently spent a few grand on the complete Topps sets from 1972 through '79. The collecting began when he was a boy; his mom once drove him six hours to Atlanta for outfielder David Justice's autograph. (Young Josh waited near the Braves' parking lot after the game only to watch Justice zoom by in his car.) Even now Donaldson remains a signature-seeking fanboy: Prominently displayed in his den is a framed Miguel Cabrera jersey, signed by the Tigers' star before a game last year.

As for Donaldson's autograph, no one is lining up for it this afternoon. Sure, in his long-sleeve T-shirt, workout pants and backward camo baseball cap, he is, in his words, "just another average white guy, if you walk by me on the street." But Donaldson, in his first season in Toronto after six in the A's organization, has been the best player on the team—he has, in fact, been one of the best players this year in the entire American League. And still he can walk in and out of this café, just blocks from the Rogers Centre, unnoticed. Not even the dude wearing a Jays hat does a double take.

"The card I want is the '51 Mantle," the 6-foot, 220-pound Donaldson is saying over the lunchtime bustle, when he's asked what he'd add to his collection if he weren't also the most underpaid player in baseball (an MLB minimum $500,000 last year; awarded $4.3 million in arbitration this season). "That's his rookie card, and depending on the condition, it can be over a million dollars. It's funny, memorabilia now is on another level—the cards are way better than when I was growing up. But I miss how the older-minted cards felt: the dingy feel, the clean look, the color popping out of the uniforms."

This Donaldson—the geek who in a card store turns as giddy as a 15-year-old at a One Direction concert—may be hard to reconcile with his in-game persona: a profanity-spewing, home-run-admiring, ornery s.o.b. In May, Donaldson was caught on camera in the Jays' dugout fire-bombing the Angels with obscenities after some harmless in-game tensions boiled over. "In terms of the intimidation factor, you ask around the league and I guarantee this guy is in the top five," says Oakland third base coach Mike Gallego. "There were some guys on his own team who didn't love him. He's going to find a way to beat the other team, and if you weren't on board, he didn't have time for you."

Those who know Donaldson, though, will tell you that it all fits together—the win-at-all-costs hothead, the stickler obsessed with his craft and the nerd with a wealth of obscure baseball tales. "He just eats, breathes, sleeps and dreams baseball," says his friend and former A's teammate Jonny Gomes. "He's a nut, and a rat, all rolled into one."

IT'S HARD to think of a more dramatic reversal of baseball fortune recently: Three years ago Josh Donaldson was a fringe catching prospect, and now he's on the cusp of superstardom. His origin story takes place in spring 2012 on a hot morning in A's training camp in Mesa, Ariz. Donaldson—drafted as a catcher five years earlier by the Cubs in the first round and acquired by the A's as a throw-in player in the '08 trade that sent pitcher Rich Harden to Chicago—is clustered with the other backstops on a remote field. The third basemen are nearby, fielding bunts, and starter Scott Sizemore, charging one, gets his spikes caught in the grass and tears his ACL. Donaldson, who appeared at third sporadically in the minors, looks up at manager Bob Melvin, who gives him a nod. Donaldson takes off his gear, begins taking grounders at third and never dons the tools of ignorance again.

It's true: If Sizemore hadn't gotten hurt, there's no telling where Donaldson would be now. But what gets lost in the story is that Donaldson, who still needed to outperform the other third basemen in camp, had worked all off-season to be ready for that opportunity. He had gone to the Dominican Republic for winter ball, and told the manager there that he wanted to develop his skills at third.

"I've always needed to try to find ways to separate myself," Donaldson explains. "As someone who wasn't the biggest and the strongest, I've always thought that I had to outwork everyone else." When he was 12, he would hit into an eight-foot-by-eight-foot net in his backyard, taking 300 hacks righthanded, and 300 hacks lefthanded. At Faith Academy he would play in a football game—he was a star cornerback—and afterward meet his baseball coach to get some work in. When he'd go through hitting slumps at Auburn, he'd have his girlfriend feed a pitching machine for him during weekends.

In Oakland, while Donaldson was adjusting to third base, "We had to literally take him off the field and say, 'Let's try again tomorrow,' and he'd be upset because he didn't get it right," says Gallego. "His first-step quickness was unbelievable, his eyesight was supernatural, [and] his range would increase every single day." All those years as a catcher—knowing how to block balls in the dirt and get to his feet to throw—facilitated the transition. Still, Donaldson had to learn to read the first hop of grounders and to detect patterns in how balls would come off the bat based on the pitch.

He was a perfectionist. This quality, which he thinks hindered his development—"I just put too much pressure on myself to prove that I was capable, constantly fighting myself to do this thing that I loved and devoted my entire life to"—was sometimes misinterpreted. After batting practice, while most teammates lounged in the clubhouse using their phones or watching a movie, Donaldson would pull up a chair in the coaches' room. "Other players would think he was in there to brownnose with the coaches, and there's no doubt he would take some ribbing," says Gallego. "But he was just coming in to talk baseball. He's just the epitome of a baseball rat."

It was Donaldson's bat that always undermined him, earning him a reputation as a minor league masher who struggled in the majors—what the industry calls a "4A" player. By 2012 he felt that, like a typecast actor, he was "getting very close to that point where I'd have a label and not ever be able to get rid of it." Though he had hit .335 with a .402 on-base percentage in 234 minor league plate appearances that season, during his first 100 plate appearances in the majors he batted .153, struck out 26 times and walked once. One afternoon at Texas, early in '12, he looked up at the starting lineups on the scoreboard and an .082 average next to his name. "[Giants pitcher] Barry Zito was hitting higher," says Donaldson. "At that moment I felt like there wasn't another player in baseball that was worse than me." Donaldson was already 27, and he couldn't help feeling that he was running out of time.

That summer in the big leagues Donaldson began watching video. For most major leaguers video has become essential, but in the minors access to it is limited. In many ways Donaldson was able to see his swing for the first time, and it became clear the he was struggling with his "load process"—the timing move that gets a hitter from his stance to the swing position. A toe-tap, a small leg kick, a subtle shift of the front foot—Donaldson was always trying new techniques. While studying other swings, he locked onto the pronounced leg kick of Jays slugger Jose Bautista and began to mimic the move. Everything changed: Suddenly Donaldson was balanced and ready when the ball entered the strike zone, with time to read the pitch. He began seeing the results during the summer, first in Sacramento and then after he was called up to Oakland for the stretch run. From mid-August on, his OPS was .844. He never spent another day in the minors.

Within two years of making the switch from catcher to third base, Donaldson was one of the AL's best fielders at the position. (Last season he was one of three Gold Glove finalists, and no third baseman rated higher by advanced defensive metrics.) And within two years of being one of the worst hitters in the game, he had become one of its most valuable players: By measure of Baseball Reference's Wins Above Replacement, in 2013 and '14 only Mike Trout and Clayton Kershaw were worth more to their teams, and so far this season Donaldson ranks fourth in the AL in WAR.

IN FOOTBALL, if you get pissed off at someone, you can hit him on the next play," Donaldson says. "In baseball ... well, there's no equivalent."

He's now getting at what has been his biggest challenge, in many ways harder than changing positions or learning to hit big league pitching. Back in high school even though he was a football star, he was realistic enough to see that he didn't have a future in the NFL. The "football mentality" is part of his DNA, however, and he thinks that was a problem early in his career, when he was trying to fit into a conservative sport with unwritten rules and a buttoned-up culture. As a prospect with the Cubs, Donaldson felt stifled in an organization that, at the time, restricted facial hair and had rules on how to wear socks, regulations that Donaldson calls "eyewash."

Really, he was a perfect fit with the A's, baseball's biggest frat house, home of shaggy-haired misfits and oddballs. Donaldson became a cult hero in the Bay Area, a loud, brash leader with a faux hawk punctuated by a gnarly rattail that snaked out from the bottom of his cap. For the first time, he says, "I was told, Be yourself. Take ownership of who you are. I'd been waiting to hear those words.

"What's weird is that standards are different for every organization in this game," he says. "For me, I like to have fun, without disrespecting the other team. You see younger guys getting [to the majors] earlier, and you're seeing more emotion in the game, and sometimes it doesn't go over well. I love it." Donaldson won't apologize for an outburst like the one against the Angels or for his penchant to linger a bit longer than some pitchers appreciate after a home run swat. "I can't ever change that—I'm just slow out of the box to begin with," he says, only somewhat convincingly.

He was at home in Mobile, playing video games, when his phone exploded with texts the night of last Nov. 28. The baseball world was stunned, but the deal (for third baseman Brett Lawrie and three prospects) that sent Donaldson to Toronto didn't come out of nowhere. The A's had begun trading away assets earlier in the off-season, and because of GM Billy Beane's history of unloading players in their prime for younger talent, Donaldson had suspected his time in Oakland would end with him seeing on Twitter that he'd been traded.

Donaldson has chopped off his rattail. His vibe is not quite as renegade at the Rogers Centre, where, by contrast with Oakland's O.co Coliseum at which games feel like KISS concerts, nights in the temperature-controlled dome can resemble convention gatherings. But he has lost none of his edge, lending swagger to an offense—with himself, Bautista, Edwin Encarnacion and Russell Martin at the heart of the order—that's the highest scoring in baseball. He's still getting used to the Rogers Centre's artificial turf, which can be unforgiving—"I just have to be more respectful toward my body," he says, noting that he's become more proactive with his physical therapy. But at the plate, he's gone from an extreme pitcher's park with swirling winds (by his count, he lost 15 home runs in Oakland last year) to one of the league's most hitter-friendly. Through Sunday he ranked in the top 10 in the majors in home runs (22) and RBIs (62). "Leaving Oakland, it was ahead of schedule in terms of what I was thinking," he says, "but in the long run, the move is going to be better for my career." He won't be a free agent until 2019.

Donaldson glances at the time on his phone: There's a game tonight, and he'll have to start his extensive pregame preparation soon. But he has time for one more card story. When he was in elementary school, he saved up three dollars in lunch money to buy the rookie card of his favorite player, Braves outfielder Ron Gant. Donaldson showed up at the card store not far from his school, only to be told by the man behind the counter that he was seven dollars short; after begging his mother for the difference, he returned and bought the card. He put it in Bubble Wrap. "It was my prized possession," he says.

Not long ago he was on the field before a game in Seattle when he was called over by some fans in the stands. They had somehow heard the story of his now worn-out Gant card, and they had come to the ballpark to give him that same card—one in pristine, mint condition. Donaldson was grateful, and more than happy to give these kind strangers the simple thing they wanted in return: his autograph.

"In terms of the intimidation factor, you ask around the league and I guarantee this guy is in the top five," says Gallego.

"You're seeing more emotion in the game, and sometimes it doesn't go over well," Donaldson says. "I love it."

QUICK HITS

20.3

Donaldson's Wins Above Replacement since 2013, second in the AL only to reigning MVP Trout's 22.8.

67

Donaldson's runs scored, third overall in the majors and three off Brian Dozier's lead of 70 through Sunday.

22

Home runs for Donaldson, ninth in the majors (Harper, Trout and Giancarlo Stanton lead with 27 each) and fifth in the AL.

PHOTOPhotograph by Tim Clayton For Sports IllustratedV-JAY DAY Halfway through the season, the trade that brought Donaldson to Toronto for Brett Lawrie and prospects is looking like highway robbery for the Jays. PHOTOBRACE HEMMELGARN/MINNESOTA TWINS/GETTY IMAGESTHROW DOWN By most defensive metrics, including UZR and Defensive Runs Saved, Donaldson is the best third baseman in the stacked AL since the start of last season. PHOTOWILL VRAGOVIC/TAMPA BAY TIMES/TNS/LANDOV[See caption above] PHOTOTIM CLAYTON FOR SPORTS ILLUSTRATED PHOTOTOM SZCZERBOWSKI/GETTY IMAGESBOMB SQUAD Donaldson (tongue out) and a homer-happy offense helped keep the Jays at .500 despite a team ERA of 4.10.

HOLE YARDS PAR R1 R2 R3 R4
OUT
HOLE YARDS PAR R1 R2 R3 R4
IN
Eagle (-2)
Birdie (-1)
Bogey (+1)
Double Bogey (+2)