Jason Collins, a 35-year-old N.B.A. center who announced last year that he was gay, signed a 10-day contract on Sunday to join the Nets.
The signing is likely a significant step toward transforming North American professional sports into a more welcoming environment for gay athletes. No N.B.A. game has taken place with an openly gay player on the floor. The N.F.L., Major League Baseball and the N.H.L. — the continent’s other three traditional major sports leagues — have also never had a publicly gay participant.
The very act of Collins’s suiting up and stepping onto the court, then, would represent a milestone in the effort to change a sports culture that some feel has lagged far behind society at large in acceptance of gay people. Collins was listed as an active player for the Nets’ game Sunday night against the Los Angeles Lakers at Staples Center.
It also seemed noteworthy that the first openly gay player in one of America’s major sports leagues would play for a Brooklyn team. In 1947, Jackie Robinson of the Brooklyn Dodgers became the first black player in baseball.
And it felt significant, too, that the Nets’ owner, Mikhail D. Prokhorov, is from Russia, where President Vladimir V. Putin has come under intense scrutiny for a law that bans “gay propaganda.”
“Today Jason Collins tore open the last remaining closet in America,” said Brian Ellnor, a founding member of Athlete Ally, a nonprofit that raises awareness about homophobia in sports. “This is a piece of history, an important point on the continuum toward justice and a moment to celebrate.”
Many felt that such a moment was overdue. Last April, after spending the 2012-13 regular season with the Boston Celtics and the Washington Wizards, Collins announced in a Sports Illustrated article that he was gay. He was met with widespread support and earned a measure of celebrity — but not a new contract to play basketball. He was not invited to any team’s training camp and spent the last several months working out at his home in Los Angeles, readying himself in case a team called.
Collins’s arrival with the Nets began to take shape two weeks ago, when he worked out for them in Los Angeles over the All-Star break. The Nets, who need help with interior defense and rebounding, were also interested in Glen Davis, who was bought out of his contract last week by the Orlando Magic. With Davis appearing to be near an agreement with the Los Angeles Clippers, though, the Nets shifted their focus on Sunday to Collins.
Collins, like any N.B.A. player, can sign two consecutive 10-day contracts before the Nets must either sign him for the rest of the season or release him.
“The decision to sign Jason was a basketball decision,” General Manager Billy King said in a statement. “We needed to increase our depth inside, and with his experience and size, we felt he was the right choice for a 10-day contract.”
Collins has never been a standout player at the professional level — he has averaged 3.6 points, 3.8 rebounds and 0.5 blocks per game in his career — but he has consistently earned plaudits for his professionalism and smarts on the court.
As a Nets player, the 7-foot, 255-pound Collins will be valued for his ability to provide a disciplined application of the coaches’ defensive scheme, to read opponents’ movements and to communicate to teammates what he sees.
Collins will be a familiar face to many in and around the organization. He spent his first six and a half seasons with the Nets, who reached the N.B.A. finals twice during his tenure. It was during that time, too, that he became good friends with Jason Kidd, who is in his first season as the Nets’ coach.
Collins, who has played for five other N.B.A. teams, played alongside Joe Johnson when the two were with the Atlanta Hawks, and spent part of last season with the Boston Celtics, playing with Kevin Garnett and Paul Pierce. Johnson, Garnett and Pierce are now his teammates.
Collins is re-entering an American sports landscape that has changed for gay athletes since he last played.
Robbie Rogers, 26, came out publicly last February while simultaneously announcing that he would retire from professional soccer. But Rogers changed course in May, joining the Los Angeles Galaxy and going on to play 11 games last season.
And this month, Michael Sam, 24, announced that he was gay shortly after completing a four-year college football career at Missouri. Football analysts expect Sam, a highly regarded defensive lineman, to be selected in May at the N.F.L. draft.
“Jason told us that his goal was to earn another contract with an N.B.A. team,” the league’s commissioner, Adam Silver, said in a statement. “Today, I want to commend him on achieving his goal. I know everyone in the N.B.A. family is excited for him and proud that our league fosters an inclusive and respectful environment.”