Former Atlanta Hawks reserve Jason Collins made history Monday, becoming the first male professional athlete on a major U.S. team sport roster to publicly disclose his homosexuality.

"I'm a 34-year-old NBA center. I'm black. And I'm gay," Collins announced in a first-person narrative posted on si.com. His story will appear in the May 6 issue of Sports Illustrated.

Collins spent three years with the Hawks, leaving as a free agent after the 2012 season.

“Jason represented everything that we look for as a member of the Atlanta Hawks and we are proud he wore our jersey,” the team’s managing general partner, Bruce Levenson, said in a statement.

Collins spent most of the just-concluded NBA regular season with Boston, appearing in 32 games before being traded to Washington — his sixth team since entering the league in 2001 with the then-New Jersey Nets.

“If you’re in the league, and I haven’t been your teammate, I surely have been one of your teammates’ teammates,” Collins wrote on si.com. “Or one of your teammates’ teammates’ teammates.”

The former Stanford All-American, whose twin brother Jarron also played in the NBA, spent the first 6-1/2 years of his career with New Jersey, helping lead them to consecutive Eastern Conference championships. He’s known as a “pro’s pro” — “I take charges and I foul,” Collins said in SI.

Former Hawks forward Damien Wilkins was one of many current and former NBA players offering words of encouragement for the southern California native.

“Very proud of and happy for one of the coolest and most down to earth guys I know @jasoncollins34,” tweeted Wilkins, who played in Atlanta during the 2010-11 season.

Kobe Bryant, Steve Nash, Jason Kidd and Baron Davis also tweeted messages of support to Collins.

In a statement, Commissioner Daniel Stern praised Collins as an “exemplary member of the NBA family.”

“Jason has been a widely respected player and teammate throughout his career and we are proud he has assumed the leadership mantle on this very important issue,” Stern said.

Collins said he first considered coming out while with the Hawks in 2011 during the prolonged labor dispute between players and management.

“I realized I needed to go public when Joe Kennedy, my old roommate at Stanford and now a Massachusetts congressman, told me he had just marched in Boston’s 2012 Gay Pride Parade,” Collins wrote. “I’m seldom jealous of others, but hearing what Joe had done filled me with envy. I was proud of him for participating but angry that as a closeted gay man I couldn’t even cheer my straight friend on as a spectator. What a shame to have to lie at a celebration of pride.”

He continued, “I want to march for tolerance, acceptance and understanding. I want to take a stand and say, ‘Me, too’.”

Collins said he hopes to continue playing in 2013, adding he has “no idea” how teammates will respond to him.

“I hope for the best and plan for the worst,” he said. “Still, if I’m up against an intolerant player, I’ll set a pretty hard pick on him. And then move on.”

Celtics Head Coach Doc Rivers said Collins still has some basketball left in him.

"I'm really proud of Jason," Rivers told SI. "He'll be active in our league, I hope, and we can get by this — get past this. I think it would be terrific for the league. More than anything, it would just be terrific for mankind, my gosh."

Fan reaction could prove to the most problematic for Collins. Though he received considerable plaudits from the Twitterverse on Monday, there were plenty of detractors, too.

“I don’t mind if they heckle me,” Collins said. “I’ve been booed before. There have been times when I’ve wanted to boo myself. But a lot of ill feelings can be cured by winning.”

Though other gay athletes have come out after their careers ended, like longtime NBA forward John Amaechi and former Falcons offensive lineman Esera Tuaolo, none disclosed their sexual orientation while still active — publicly, at least.

Glenn Burke, a reserve outfielder with the Los Angeles Dodgers and Oakland Athletics from 1976-79, was out to teammates but told the New York Times after his career ended, “Prejudice drove me out of baseball sooner than I should have.”

“I’m glad I’m coming out in 2013 rather than 2003,” Collins wrote. “The climate has shifted; public opinion has shifted.”

Earlier this month Brittney Griner, the first overall pick in the WNBA draft, announced she is gay. Days later she snagged a lucrative endorsement deal with Nike.

“I’ve always been open about who I am and my sexuality,” Griner said, adding “it’s no big deal.”