CHICAGO -- If you’re looking for a smile from Ian Happ, you'll have to look real close. They don't come often.

The infielder-outfielder has hit 12 home runs this season -- the second-fastest Chicago Cubs rookie to reach double digits -- but you rarely know when he has crushed one from the deadpan expression on his face as he rounds the bases. In fact, it's that demeanor that stood out to the Cubs brass when they were considering drafting him in the summer of 2015.

"He's very serious about his craft," general manager Jed Hoyer said this week. "He talks baseball very seriously. He's a very serious person, really intelligent and focused."

The seriousness is a good thing, considering that the reigning World Series champs are leaning on the 22-year-old as they try to find their championship level of play again. Happ's go-ahead, two-run single in the seventh inning of Wednesday's 7-3 win against Tampa Bay again proved why the club is turning to him, as he upped his remarkable .385/.429/.615 slash line late in games that are deemed late/close.

Consider this: Happ has started games in all three outfield positions as well as at second base, and he has batted no lower than sixth in the order this season. Remember when Addison Russell arrived on the scene in 2015? Joe Maddon hit him ninth to protect him, to hide him from all the pressure and let him see better pitches behind the pitcher. That hasn't been the case with Happ.

"Part of that was out of necessity," Maddon said. "Because I would much rather have protected him, no question. He's responded really well."

That necessity came when the injuries started to pile up, and Kyle Schwarber's underachieving performance has also allowed the switch-hitter to shine.

All Happ has done is lead the Cubs in OPS with a .906 mark. On a team with the reigning National League MVP in Kris Bryant and a three-time All-Star in Anthony Rizzo, it's Happ who has been the most dangerous.

Ian Happ is batting .269 with a club-leading .906 OPS. Patrick Gorski/Icon Sportswire

"[He] runs better than people know," Maddon said. "As he gets on base more consistently, this guy can steal some bags, I think."

Happ is the fastest Cub, according to Statcast, which recently released speed ratings for baserunners. Maddon hasn't ruled him out as a future leadoff hitter, as his power-speed combination is already standing out.

"He's so athletic," first base and outfield coach Brandon Hyde said. "He plays with confidence in the outfield, with little experience. He walked in with confidence."

Happ quietly declared that he belonged in a big league clubhouse during spring training, when he was given a locker next to Jon Lester and John Lackey. He "earned it," as he said back then.

He continues to earn it, as he led the Cubs in home runs in June, with eight. He already has two multi-home-run games, while committing just one error so far.

That last point is a source of pride for Happ, whose already-serious face grows even sterner when the topic of defense arises. That was the knock on him when he was drafted and while he was coming up. Where would he play? Could he play it well enough? Even Maddon doubted him.

"In spring training, seeing him at second base, I did not think it was going to work," Maddon said bluntly. "I'll be the first one to tell you that. He's proven me absolutely wrong."

Happ has proven many wrong on defense, simply because he's so athletic. It's not always pretty -- he's learning four positions at the big league level -- yet you would be hard-pressed to find a play he should have made but didn't.

"There's always going to be questions, 'Can he do this, or can he do that?'" Happ said. "'Can he play infield? Can he play outfield?' I’ve always been confident in my ability to play multiple positions."

Hyde expressed confidence in the rookie, adding that Happ "is going to be a special defender."

"One of the best things about Ian is he does have a chip on his shoulder, but he carries it well," Hoyer added. "He wants to prove people wrong. He believes in himself. This guy is a good athlete. That was the talk around the draft. If he's an athlete and is willing to work, he can be a good defender."

Right now, Happ seems like a natural at the plate. After a torrid start, he went into the typical rookie slump. But rather than being sent back to the minors, he played his way out of it.

"It's baseball," Happ said. "You're going to have a week or two you don't feel good. You're going to have weeks where you feel great."

Everything about Happ screams that he's mature for his age, and he has shown that savvy off the field as well. No other Cub has held two news conferences in road cities this season, as Happ did in Pittsburgh (his hometown) and Cincinnati (where he starred at the University of Cincinnati). When team media relations personnel started looking to bring him out to the dugout in Pittsburgh, Happ was already there doing his interviews. He gets it.

"This division is awesome," Happ said. "A bunch of great ballparks, a bunch of great teams to play. It doesn't get better than that. I get to go home three times a year."

That's as long as he remains a Cub. He was considered trade bait for a while, but it's hard to see the Cubs without him now. But when is the serious-faced rookie going to break out the smile that has become a trademark in Chicago's clubhouse during Maddon's tenure?

"I've seen it," reliever Pedro Strop said with a smile of his own. "Around [the clubhouse] or on the bus. Or when we celebrate after a win. He smiles. He's having fun."

Added Happ: "I do smile -- sometimes."