"Can't do that," the 33-year-old corner infielder said, laughing. "They're both good."
There's no question Trout, the Angels' 22-year-old center fielder, has had the better career thus far, finishing second to Miguel Cabrera for the American League's Most Valuable Player Award in back-to-back seasons and gaining widely-held recognition as the best all-around player in baseball.
But Harper, the Nationals' 21-year-old corner outfielder, has posted a .272/.353/.481 slash line with 42 homers the last two years and continues to get better.
The pair -- both Rookie of the Year Award winners in 2012 -- have constantly been compared, from the time they came up through the system to their stint on the Arizona Fall League's Scottsdale Scorpions in 2011 to the 2012 All-Star Game they both played in the following July.
But they couldn't be any more different, from their demeanor to their style of play to their overall success.
The biggest difference, Tracy says, lies in their swings.
"I think Harp's swing provides the higher, longer-type home run when he makes contact," Tracy said. "Trout, he hits the hard line drives that either knock the infield down or if he just misses it then he knocks it out of the park. It just seems like the long, majestic home runs in BP are not his deal. He tends to use less energy and work on a nice, short, smooth stroke during batting practice, and then in the games the same swing provides line-drive home runs.
"They're both really mature for their age. I haven't really interacted with Trout off the field yet; it's all been in here. But I know for a fact that Harp's a really good kid, and it seems the same with Mike, too. He's very energetic. He seems like he gets along with everybody."
Alden Gonzalez is a reporter for MLB.com. Read his blog, Gonzo and "The Show", and follow him on Twitter @Alden_Gonzalez. This story was not subject to the approval of Major League Baseball or its clubs.