Colon, 44, an All-Star last season with the New York Mets, had been a disappointment this season, going 2-8 with an 8.14 ERA.
He returned Wednesday after being on the disabled list since June 6 for a strained oblique and a stiff back. Colon gave up six runs on eight hits and three walks over four innings of a 7-4 loss to the Padres -- the third straight start in which he failed to reach the fifth inning.
"I felt good, I just feel like I've kind of hit a rough streak, to be honest, and it's tough to just snap out of it," Colon, who is from the Dominican Republic, said through a translator after the game. "The reality is that I've been getting hit hard and that's the truth and you can't dance around it."
Colon, who lost for the sixth time in his past eight starts, had surrendered at least five earned runs in seven of his 13 starts this season. He signed a $12.5 million deal with the Braves prior to the season.
"We hated to do it,'' Braves manager Brian Snitker said of releasing Colon. "It wasn't easy because he is such a great guy and a wonderful teammate. But it just wasn't happening here.''
Unless Colon is traded or claimed on waivers, the Braves would be responsible for the remainder of his salary. If he is released and signs with another team, the new club would be responsible for only a prorated share of the $535,000 minimum.
"He's had a great career and he beat the odds for a while,'' Snitker said. "He was very appreciative of everything and I wish him nothing but the best.''
Mets manager Terry Collins didn't indicate whether the Mets would be interested in a return.
"He has had an absolutely tremendous career," Collins said. "I'm sure he'll land on his feet someplace. He's a pretty valuable guy to have."
A veteran of 19 major league seasons, Colon has a career record of 235-170 with a 4.02 ERA and 2,407 strikeouts. His win total ranks third among Latin American-born pitchers, trailing only Nicaraguan Dennis Martinez (245) and fellow Dominican Juan Marichal (243).
Colon's successful run with the Mets from 2014-16 helped affirm his status as one of the game's most durable and popular players. He began his career with Cleveland in 1997 and won his Cy Young Award with the Angels in 2005.
Colon is a four-time All-Star, most recently with the Mets last year, when he won 15 games with a 3.43 ERA.
The Braves hoped Colon could serve as a fill-in for a year while the team waited for pitching help from prospects still in the minors. One of those prospects, left-hander Sean Newcomb, has a 1.48 in his first four starts, including a win over the Padres on Tuesday night.
But Colon's ability to retire hitters on guile and guts hit an obstacle with the Braves.
"The movement wasn't there, the location and just how he survived before,'' Snitker said.
"He started struggling in spring training a little bit, but you kind of write that off as spring training. You don't worry about it.
"But he just wasn't real good here and he couldn't get over the hump.''
Thanks to Newcomb's arrival, no adjustment to the rotation will be needed. The Braves had planned on a six-man rotation with Colon's return on Wednesday, but now they can return to their normal five-man staff of starters with Julio Teheran, R.A. Dickey, Newcomb, Mike Foltynewicz and Jaime Garcia.
To fill the spot on the roster, the Braves called up left-handed pitcher Rex Brothers from Triple-A Gwinnett.
Brothers, 29, allowed no runs in four relief appearances with Gwinnett. His last major league appearance was with Colorado in 2015. He saved 19 games for the Rockies in 2013 and has a 3.42 career ERA.
The Associated Press contributed to this report.