That's when you begin to understand how good he really is. How he relentlessly plays the game the right way.
Yes, that's a cliche, and you know how some sportswriters love their cliches. In Prince's case, it means he sweats the small stuff.
He runs out every single ground ball, no matter how routine. He's also a smart baserunner. He understands game situations, too.
If you only catch Prince now and then, you might see him as a slugger and nothing more. He's that, too.
He has a beautiful swing that produces massive power. He has the kind of swing other players admire.
For instance, Ryan Braun.
When Prince's former teammate was asked to pick a winner in the Home Run Derby on Monday, he didn't have to think long.
"If Prince is in it, I'm picking Prince," Braun said.
"If Prince is playing anything, I'm picking Prince," he added.
Ding, ding, ding.
Prince won the Home Run Derby for the second time in four years Monday night, with 28 long balls averaging 432 feet.
He launched towering shots that disappeared into the warm Missouri evening and landed far over the fence in right field and right-center.
He made it look so easy, didn't seem to be swinging hard. He's so locked in and so smooth that he doesn't seem to be trying.
Prince has had an interesting career. He sprinted through the Minor Leagues, joining the Brewers after fewer than 500 games.
He was an All-Star in just his second full season, and has been one of the players others are measured against ever since. He has missed one game the past three seasons, and eight seasons later, has never changed his approach.
He's not always the most open of interviews, seemingly could take or leave the fame that comes with being a high-profile player in the Major Leagues.
That stuff aside, you can ask two dozen scouts and opposing managers about Prince, and they virtually all say the same thing.
He plays hard. He cares about the right stuff. He wants to be great and isn't going to take a shortcut.
This season has been an interesting season for Prince. His nine-year, $214 million contract with the Tigers removed him from the comfort zone he'd established in Milwaukee.
It also put the kind of expectations on him he hasn't really had before. Some of us penciled Detroit into the World Series before the first pitch of Spring Training was thrown.
Tigers manager Jim Leyland warned us against making anything sound easy, and, indeed, it hasn't been easy.
It hasn't been easy for Fielder, either. His numbers are down almost across the board, and at times things appear to have come hard for both Prince and his teammates.
That's why this All-Star break may be good for him. It's a chance to get away, to take a deep breath and to start over in the second half.
He could have passed for the happiest man on earth Monday as he bounced through a busy day with his two young sons at his side.
And then he finished it off with a dazzling performance in the Home Run Derby. Here's hoping this was a good start on a great second half.
Richard Justice is a columnist for MLB.com. Read his blog, Justice4U. This story was not subject to the approval of Major League Baseball or its clubs.