In this year's new format, Chicago Cubs rookie Kris Bryant is in a pairing with the Los Angeles Angels' Albert Pujols, Toronto's Josh Donaldson is in a bracket with the Chicago Cubs' Anthony Rizzo, and Los Angeles Dodgers rookie Joc Pederson takes on Baltimore's Manny Machado.
The Frazier-Fielder winner faces Donaldson or Rizzo, and the Bryant-Pujols winner goes against Pederson or Machado.
Brackets were based on season home run totals through Tuesday.
Each batter gets five minutes per round, and home runs in each batter's final minute stop the clock. Players can earn up to 1 minute, 30 seconds of bonus time based on home run distance.
"Swinging for five minutes, that's going to be a really long time. Really long," Pederson said. "Hopefully I don't have to go first and I can watch how some of the veterans go about it."
Pederson has selected Triple-A coach Johnny Washington to pitch to him.
"He's been with me since Day 1," he said. "It's only appropriate that he gets to come along and gets to share in this event, see how far we've come together."
Bryant said his father, Mike, will throw to him. Mike Bryant taught Kris to hit at a young age, passing along the lessons he learned from Ted Williams during the two spring trainings he was a Boston Red Sox farmhand in the early 1980s.
"I'm probably doing it more for him so he can experience it with me," Kris Bryant said Wednesday. "We always talked about it growing up and now it's here."
Bryant thinks Rizzo may have an advantage at Great American Ball Park.
"Cincinnati's a pretty good left-handed hitter's ballpark," Bryant said. "Hopefully, I win it, but if he wins, that's great, too."
Fielder won the derby in 2009 and 2012. He will be participating for the sixth time, matching Barry Bonds and Sammy Sosa, and trailing only Ken Griffey Jr. and Mark McGwire.