Chacin, 1-2 with a 5.40 ERA in five starts this season, had been scheduled to start for the Braves on Wednesday night against the Phillies. The Braves have recalled right-hander Williams Perez, 24, from Triple-A Gwinnett to make the start.
"The thing I'm excited about with the trade is we get to put Williams Perez in the rotation," Braves manager Fredi Gonzalez said. "We're excited to add him to our rotation and get younger. That's what we wanted to do."
The Braves removed another veteran from the rotation last month when Bud Norris was shifted to the bullpen.
The youth movement is expected to continue this season for the struggling Braves (7-23), who took a five-game losing streak into Wednesday night's game.
Among other top prospects at Gwinnett are shortstop Ozzie Albies, who was recently promoted from Double-A Mississippi, and third baseman Rio Ruiz.
"There are a couple of guys out there making noise," Gonzalez said. "Sure, we want to get younger. ... I can't give you a schedule of when those guys will be here. I've always been a big believer they'll let you know when they're ready."
McCreery, 23, pitched the last two seasons for rookie-level Tempe in the Arizona League. He is in extended spring training.
The 6-foot-8 McCreery posted a 3.52 ERA in 31 appearances, all in relief, the last two years.
Chacin, 28, was in his first season with the Braves. He signed with the team as a minor league free agent after spending six seasons with Colorado and one season with Arizona.