A few familiar faces joined the thousands of protesters who marched from Roxbury to the State House in Boston last week to speak out against racism and police brutality after the killing of George Floyd at the hands of officers in Minneapolis.

"We've got Marcus Smart and we've got Vincent Poirier right there, here to support us,” protest organizers told the crowd on May 31. “The same way we support them every single night, they're here to support us."

The two Celtics, who were at the front steps of the State House with protesters, weren't the only ones joining such demonstrations. Their teammate Enes Kanter also joined marchers that day. Another, Jaylen Brown, led a protest in Atlanta the day before.

"Being a celebrity, being an NBA player don't exclude me from no conversations,” Brown said on a video on his Instagram account. “First and foremost, I'm a black man and I'm a member of this community and I grew up on this soil."

As the country mourns the killing of George Floyd, Breonna Taylor, Ahmaud Arbery and other African Americans, professional athletes have been voicing their discontent with the racial status quo. It's not just the Celtics. Players throughout the NBA and other pro leagues — locally and nationally — have been using their voices to call for change.

Celtics Coach Brad Stevens spoke to reporters last week and praised his team’s players for speaking out.

"We want them to stand for what they believe in and we want to be supportive of that,” he said. “And that's been clear the whole time I've been there, but it's been reinforced over and over and over ... and I think that that's been a big part of why I've enjoyed working here so much."

Players, coaches, teams — the Celtics, Red Sox, Patriots and Bruins have all issued statements and the New England Revolution and Boston Pride have also expressed support for those demanding justice — and even leagues are supporting the protests. And public condemnation has been heaped on those who aren’t supportive.

New Orleans Saints Quarterback Drew Brees drew widespread backlash when he told Yahoo Finance that he wouldn’t agree with anybody “disrespecting the flag of the United States of America,” referring to NFL players kneeling during the national anthem. He later apologized, saying the comment “completely missed the mark on the issues we are facing right now as a country.”

On June 4, multiple NFL players, including Stephon Gilmore of the Patriots, appeared in a video demanding the league formally condemn racism, admit it was wrong in attempting to silence player protests and state the NFL believes Black Lives Matter.

That led NFL Commissioner Roger Goodell to issue a statement the next day via a video on Twitter meeting the players' demands and making his most outspoken statements on racism and police brutality to date.

“Without black players, there would be no National Football League,” he said. “And the protests around the country are emblematic of the centuries of silence, inequality and oppression of black players, coaches, fans and staff.”

As players have called for more actions, some franchises have stood behind them. But it’s coming at a time when that stance has become the norm, even for businesses that historically may have been quiet about racial issues.

"It's in their best interest, business-wise, to adopt that type of posture,” said Joseph Cooper, a professor at UMass Boston who studies sports and race.

Cooper said what really matters is what happens when protests aren't convenient, when institutions are challenged to follow up a Twitter statement with action or when a human rights stance isn't in franchises' best business interests.

"If you're serious, you're gonna partner with organizations that are doing the real work, even when it's not mainstream,” he said.

Cooper said historically, individual athletes have shouldered the burden of speaking up. He wants to see the organizations that make up professional sports embody a human rights mentality.

"Organizations, this is another golden opportunity where it's mainstream to champion human rights. You could make that pivot right now and it wouldn't cause a lot of stir. So I would think this would be the most opportune time for those organizations to do this, to make that pivot and to sustain it moving forward," he said. "My knowledge of the history of sport and the history of this country is that this is more than likely going to be a short-term, symbolic act and then it'll be back to business as usual once things die down. Unless athletes, spectators and our other members of society demand that it changes."

Some organizations are already getting started. For example, the Patriots announced on June 5 that the Kraft family is pledging $1 million in $100,000 monthly donations over the next 10 months to local grassroots organizations that work for equity and the end of systemic racism.