And NFL player Brendon Ayanbadejo, The New York Times reported, has been in contact with closeted players in several sports.
"What we're trying to facilitate is to get them together and do what they want to do, do what is right for them," he told the Times.
In February, former professional soccer player Robbie Rogers announced on his blog that he is gay. His former U.S. teammates showed solidarity in response to the news.
Though reaction to Collins' announcement also was overwhelming support, not everyone had a positive response.
ESPN basketball analyst Chris Broussard said the Bible calls homosexuality a sin.
"If you're openly living in unrepentant sin, whatever it may be, not just homosexuality, adultery, fornication, premarital sex between heterosexuals, whatever it may be. I think that's walking in open rebellion to God and to Jesus Christ," he said.
NFL receiver Mike Wallace tweeted Monday: "All these beautiful women in the world and guys wanna mess with other guys SMH."
He tweeted again, saying he was being misinterpreted.
"Never said anything was right or wrong I just said I don't understand!! Deeply sorry for anyone that I offended," he wrote.
The Dolphins, Wallace's employer, issued a statement saying the team has spoken with Wallace about the tweets. The team said it will address its policy of inclusion with all of its players.
NBA Commissioner David Stern said Collins, a 34-year-old veteran, is widely respected in the league.
"We are proud he has assumed the leadership mantle on this very important issue," he said in a statement.
Washington Wizards President Ernie Grunfeld said the team is "extremely proud of Jason and support his decision to live his life proudly and openly."
"He has been a leader on and off the court and an outstanding teammate throughout his NBA career. Those qualities will continue to serve him both as a player and as a positive role model for others of all sexual orientations," Grunfeld said.
Boston Celtics head coach Doc Rivers called Collins "a pro's pro" and one of his favorite players he ever coached.
"If you have learned anything from Jackie Robinson, it is that teammates are always the first to accept," Rivers said. "It will be society who has to learn tolerance."
Bill Clinton called the announcement an "important moment for professional sports and in the history of the LGBT community."
Collins, who had been traded by the Celtics to the Wizards this season, wrote in his essay that U.S. Rep. Joe Kennedy, D-Massachusetts, helped prompt his decision to come out as gay. Kennedy and Collins were roommates at Stanford. He recounts hearing about Kennedy, who is not gay, marching in Boston's Gay Pride Parade.
"For as long as I've known Jason Collins he has been defined by three things: his passion for the sport he loves, his unwavering integrity, and the biggest heart you will ever find," Kennedy said. "I'm proud to stand with him today and proud to call him a friend."
President Barack Obama called Collins "to express his support and said he was impressed by his courage," a White House official said.