Young Orioles third baseman Manny Machado is wowing the American League with his bat, but he's even more elite with his glove.
A.J. Pollock wasn't supposed to be the D-backs' center fielder at the beginning of 2013, but now he's among the best at fielding his position in Major League Baseball.
And Andrelton Simmons? The Braves' second-year man is the best shortstop in the sport, and it isn't even close.
These are theories, of course. Not unassailable facts. Not yet, at least.
They're assertions backed up by numbers, to be sure, and as the intricate art and science of quantifying defensive value in baseball continues to evolve, they will continue to spawn discussions and arguments about what the stats tell us and what our eyes show us.
So given all that, who are the best defenders in baseball, according to the numbers?
Well, it depends on who you ask.
Ultimate Zone Rating (UZR), developed by Mitchel Lichtman, quantifies the number of runs a fielder is above or below average, according to FanGraphs.com, where the stats are accessible, by combining "range runs" -- "the number of runs above or below average a fielder is, determined by how the fielder is able to get to balls hit in his vicinity" -- and "error runs," defined as "the number of runs above or below average a fielder is, determined by the number of errors he makes as compared to an average fielder at that position given the same distribution of balls in play."
According to UZR entering Friday, Machado is leading the Majors at 10.9, with Brewers center fielder Carlos Gomez second at 9.1, Pollock third at 8.8, Tigers left fielder Andy Dirks next at 7.9 and Simmons fifth at 6.8. In the team category, the Kansas City Royals have the best club UZR in the game at 21.0.
Machado is an intriguing case since he was expected to be a Major League shortstop but has played primarily at third since exploding onto the scene in Baltimore last year. Entering Friday, he also was a big-time force with the bat, hitting .320 with a league-leading 26 doubles and 31 RBIs. He doesn't turn 21 until July 6, and he doesn't seem to be grabbing all the headlines, either.
"If you ask Manny, he's OK without having the hype and just doing his job, and letting everybody kind of discover him over the course of the season," Baltimore reliever Darren O'Day said. "He's starting to get [more attention] now. I know all the stat geeks love him because of the defense he plays. I know all his pitchers love him. I think all in due time, it will come."
The stat geeks do love him, and they also love Gomez, Pollock, Dirks and Simmons.
Simmons, in fact, is considered the premier defender in all of baseball according to another respected metric, Defensive Runs Saved, developed by The Fielding Bible's John Dewan.
Dewan's company, Baseball Info Solutions, employs "scouts" who pore over video of every game played in the course of a 162-game MLB season and track each batted ball. They are tasked with analyzing how hard balls are hit, how close or far they are from the fielders deemed to be responsible for making the plays, and the result of those plays. The company comes up with a number, plus or minus, of how many runs per season a fielder "saves" or "costs" his team.
According to these calculations, Simmons has saved 14 runs this year. Machado and Gomez are next with 12 each. Other positional leaders are catcher Russell Martin (eight), first baseman Paul Goldschmidt (nine), second baseman Dustin Pedroia (nine), left fielder Starling Marte (nine), center fielder Gomez (12), with Pollock next at 11 and right fielder Norichika Aoki (10). Several pitchers are tied for the lead with four runs saved.
So what does it all mean? It's hard to say at this point of the year, but it's clear that these players are off to great starts.
"Defensive stats are not perfect, but they're getting more refined," said Eno Sarris of FanGraphs.com. "It's a little volatile year to year, but so is any stat.
"For example, Simmons hasn't been in the league that long. Maybe he's starting out hot but he won't continue it for the rest of his career. Gomez has been at the top of the leaderboard for his whole career.
"Machado looks like he could be one of the premier defenders in baseball, and in his case, it probably helps him because conventional wisdom and statistics tell us third base is easier to play than shortstop. So there are a lot of variables."
The variables will continue to be worked out, but most statisticians agree that the metrics continue to improve.
The beauty of baseball, be it new-school or old-time hardball, is that a number on a page still can't replace what you see in action on a diamond.
That's why even Sarris admits that a defender's inherent feel for where a ball will be hit or knowledge culled from the experience of absorbing thousands of innings' worth of hitters' tendencies are things you just can't quantify.
"[Giants shortstop] Brandon Crawford told me that he's been behind the same pitchers forever, so he knows where to be," Sarris said.
"That's pretty good knowledge to have."
Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB.