"I didn't set out to be the first openly gay athlete playing in a major American team sport," NBA player Jason Collins wrote in Sports Illustrated on Monday. "But since I am, I'm happy to start the conversation."

In coming out, Collins shared a sentiment that many gay ex-players have also expressed: They didn't want to publicly declare their homosexuality while still actively playing because they didn't want to be a distraction to their teams. But now, at a time when 58 percent of America supports gay marriage, it might not be as big of a deal.

"I'm glad I'm coming out in 2013 rather than 2003," Collins wrote in Sports Illustrated. "The climate has shifted; public opinion has shifted." Here, a brief look at just how much attitudes toward gay marriage have shifted in major American sports:

David Kopay becomes the first ex-player in one of America's major men's sports — baseball, basketball, football, and hockey — to come out after retirement. The former running back announces he is gay after reading hate-mail written to the now defunct Washington Star over a story quoting an anonymous gay NFL player — who just so happened to be Jerry Smith, a former Washington Redskins teammate Kopay once had a sexual encounter with. Kopay would later publish The David Kopay Story: An Extraordinary Self-Revelation. After coming out, Kopay believed he was blacklisted as a potential coach because of his sexual orientation.

Ex-NFL player Jerry Smith announces that he has AIDS. He dies of the disease two months later. 

Dave Pallone, a National League umpire for 10 years, is fired by baseball commissioner Bart Giamatti. Pallone would later say in his book Behind the Mask that he was let go because he was gay.

Roy Simmons, a former NFL guard who went to the Super Bowl in 1984 with the Washington Redskins, admits that he is gay on The Phil Donahue Show. Five years later, he would find out that he is HIV positive.

Glenn Burke, a former baseball player who has AIDS, dies. He was once reportedly offered $75,000 by the Los Angeles Dodgers to get married as a way to disguise his sexual orientation. He was eventually traded to the Oakland A's, where he reportedly faced discrimination and ridicule in the clubhouse.

Atlanta Braves pitcher John Rocker gets heat in the media for saying the following about the possibility of playing for a New York team: "I would retire first. Imagine having to take the [Number] 7 train to the ballpark, looking like you're [riding through] Beirut next to some kid with purple hair next to some queer with AIDS right next to some dude who just got out of jail for the fourth time right next to some 20-year-old mom with four kids. It's depressing."

Separately, former outfielder Billy Bean comes out as a gay man, saying, "I only wish I hadn't felt so alone, that I could have told someone, and that I hadn't always felt God was going to strike me dead."

New York Mets catcher Mike Piazza, concerned by implications in an article in the New York Post, holds a press conference to announce, "I'm not gay. I'm heterosexual."

Separately, former NFL defensive tackle Esera Tavai Tuaolo admits he is gay on HBO's Real Sports with Bryant Gumbel.

John Amaechi, who played for five years in the NBA for the Orlando Magic, Utah Jazz, and Cleveland Cavaliers, becomes the first former NBA player to come out as gay in his book Man in the Middle.

On a radio show, former Golden State Warriors star Tim Hardaway says, "You know, I hate gay people, so I let it be known. I don't like gay people and I don't like to be around gay people. I am homophobic. I don't like it. It shouldn't be in the world or in the United States." He would later have a public change of heart and speak up for gay rights in 2011.

Steve Nash, the star point guard for the Phoenix Suns, makes a video in support of New York's push to legalize same-sex marriage.

Wade Davis, a former defensive back for the Tennessee Titans, Seattle Seahawks, and Washington Redskins, comes out as gay seven years after his retirement. He goes on to work at the Hetrick-Martin Institute, which provides support to LGBT youth in New York City.

San Francisco 49ers cornerback Chris Culliver says this just days before playing in the Super Bowl: "I don't do the gay guys man. I don't do that. No, we don't got no gay people on the team, they gotta get up out of here if they do. Can't be with that sweet stuff. Nah…can't be…in the locker room man."

Less than three months later, Jason Collins announces that he is gay, becoming the first athlete in a major American men's sport to come out while still playing. He is supported by a number of active players, including Kobe Bryant and Dwyane Wade:

NBA commissioner David Stern issues a statement saying: "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."

Sources: Chicago Tribune, ESPN (2), Los Angeles Times, NBA.comNew York Times, PeopleSports Illustrated (2)(3)(4)(5)Washington Post (2), Yahoo