Judge is set to take part in Monday night's Home Run Derby, while Harper is sitting out of the contest until next season when it comes to Nationals Park.
Harper said his under-the-radar pick to win Monday's contest is the Miami Marlins' Justin Bour.
"Freddie Freeman," Harper said. "Guy absolutely rakes. I hate watching him against us, because he kills us. Such a great player."
Harper also hailed Freeman for his unselfishness when he decided to move to third base so that the Braves could fit Matt Adams in the lineup.
"What he did for Matt Adams, that goes to show how much respect his teammates have for him," Harper said. "To move over from first base, .350 with 16 [home runs] or whatever he has. Then third base, he does a great job. Iv'e got a lot of respect for Freddie Freeman and what he does."
Freeman entered the All-Star break with 16 long balls. He's hitting a career-best .348.
"One guy I've always looked up to, just being out in California and being a Giants fan, was Buster Posey," Judge said. "Just the way he handles himself on the field and off of the field is incredible. He's the definition of a professional and getting the chance to play against him and be on the same field is going to be cool."
Posey is hitting .324 for the Giants.
The 2017 Home Run Derby starts at 8 p.m. at Marlins Park. Only 89 home runs have been hit so far at the ballpark, the third-fewest of any National League stadium.