He said he's not willing to endorse that label until it is proven in 2013.
The Upton brothers join right fielder Jason Heyward, who won a Gold Glove in 2012, in the outfield packed with power and speed.
"If we push ourselves to the next level, I feel with the extra push from each other there's no question we can be the best outfield in baseball," Justin Upton said in a telephone interview. "I'm not going to give us that label until we prove it."
The other minor leaguers headed to Arizona are right-hander Zeke Spruill, shortstop Nick Ahmed and first baseman Brandon Drury. Prado, projected to play third base for the Diamondbacks, can become a free agent after this season.
B.J. Upton, 28, signed a five-year, $75.25 million contract with Atlanta in November. Justin Upton, 25, said the brothers will be on the same team for the first time since he was a freshman in high school.
Upton said he already receives tips after his older brother sees him on TV. He said now there will be more chances for the two to help each other.
"I think from that standpoint it will be good, but I think more than anything being able to show up at the ballpark genuinely excited every day and have that energy," he said. "The more energy you can bring from the start every day, it makes you a better player."
Braves general manager Frank Wren said he expects the brothers will push each other.
"I do think it will drive them," Wren said, adding he has looked to add a player like Justin Upton for a long time.
"We've been looking for that young dynamic, right-handed, power-hitting outfielder that can hit in the middle of the lineup and makes that other team think a little bit," Wren said.
The younger Upton, who has three years and $38.5 million left on his contract, had been the subject of trade speculation throughout the offseason and vetoed a trade to the Seattle Mariners.
Prado, who joins fellow Venezuelan Miguel Montero in Arizona, made the All-Star team in 2010 as a second baseman and played mostly in left field last season. Prado was projected to move to third base for the Braves this season to replace the retired Chipper Jones.
Diamondbacks President Derrick Hall said via Twitter that the team wants to sign Prado to a long-term deal.
"This is the type of player we want in our lineup," he wrote.
The Braves didn't re-sign centerfielder and leadoff hitter Michael Bourn. Prado, the No. 2 hitter behind Bourn, had been a candidate to hit leadoff. Shortstop Andrelton Simmons now is expected to assume that role. Simmons hit .289 with a .335 on-base percentage in 49 games as a rookie last season.
Arizona had accumulated a glut of outfielders, signing Cody Ross as a free agent last month. Upton, an All-Star pick in 2009 and 2011, was the most marketable.
Upton, the No. 1 overall pick in the 2005 draft, has played five full major league seasons. Last season, he hit .280 with 17 home runs and 67 RBIs and a career-high 107 runs.
In 2011, while helping Arizona win the NL West, Upton hit .289 with career-best totals of 31 home runs and 88 RBIs and finished fourth in NL MVP voting. Overall, he's a career .278 hitter with 108 home runs, 739 hits, 147 doubles and 80 stolen bases.
Upton said he hopes to become a more consistent player in Atlanta.
"I've had a couple good years where I put up good numbers and my goal all along has been to put those years up consistently," he said. "I think now I'm in a position with Atlanta ... we can really feed off each other throughout that lineup to try to get everybody to that consistent production rate."
Delgado, a 23-year-old right-hander, had been expected to challenge for a spot in the Braves rotation. His acquisition bolsters the young pitching depth in Arizona depleted by the trade of Trevor Bauer. Delgado was 4-9 with a 4.37 ERA in 18 appearances, 17 as a starter, for the Braves. Rated Atlanta's No. 3 prospect by Baseball America the past two years, he was 4-3 with a 4.06 ERA with Triple-A Gwinnett last season.
The trade leaves Arizona with three veteran outfielders - Ross, Jason Kubel and Gerardo Parra - along with two youngsters the team feels are ready for the majors - Adam Eaton and A.J. Pollock. General manager Kevin Towers has praised Eaton's potential as a center fielder and leadoff hitter.
Johnson was acquired by the Diamondbacks on July 29 from Houston and batted .286 with seven doubles, seven home runs and 35 RBIs in 44 games with Arizona. Overall, he hit 15 homers with 76 RBIs. In Atlanta, he could platoon at third with Juan Francisco.
"Really enjoyed my time in Arizona," Johnson said in a tweet. "Thank you to the Diamondbacks organization and fans for your hospitality!"