Four years ago on Wednesday, Colin Kaepernick sat during the national anthem as the San Francisco 49ers’ starting quarterback in a protest of social injustice and police brutality. He would later kneel, and other players followed, drawing the ire of many people, including NFL team owners. The players’ peaceful protests caused the NFL to briefly — and foolhardily — institute a short-lived anthem policy in the summer of 2018.

Eventually, the majority of players stopped kneeling, and football continued.

Things dramatically changed after the George Floyd killing in late May. Black players, standing up for a community that is tired of watching the same thing happen repeatedly, banded together in a unified voice behind the causes. This culminated in a handful of the NFL’s star players putting together a video that demanded the league acknowledge the social movement’s mantra: “Black Lives Matter.” Even commissioner Roger Goodell ultimately capitulated, using those exact words.

It was a stunning admission for Goodell, who two years earlier declined to publicly back his players in a similar manner as the franchise owners he worked for essentially sought to muzzle them.

Even more stunning: In the days and weeks since, Goodell has doubled down on his new stance, saying that he wished the league had listened to Kaepernick earlier with regard to what he was kneeling about.

All of which brings us to Wednesday, when the Milwaukee Bucks’ decision to walk out on their NBA playoff game against the Orlando Magic following the shooting of another African American man, Jacob Blake, by police in Kenosha, Wisconsin, propelled us to the latest stage of the ongoing social justice awakening in America.

The timing of the NBA’s protest was sweet irony, considering Kaepernick’s protests began four years prior to the day. It’s even sweeter because Goodell’s recent words may soon put him in position to prove he believes everything he has been saying lately.

Two more NBA playoff games were canceled Wednesday due to the walkout, as well as multiple MLB games. And based on the early reaction of NFL players to the Bucks’ walkout, one can’t help but wonder if we’ll see NFL players threaten to do the same.

“Anything’s possible,” Seattle Seahawks coach Pete Carroll said Wednesday, when asked if the Seahawks — or any other NFL team — will end up forfeiting a game this year due to a walkout. “This is a protest season.”

Less than an hour after the Bucks walked out, Houston Texans receiver Kenny Stills tweeted that it’s “time to connect with local activists to help formulate demands,” while Kansas City Chiefs safety Tyrann Mathieu tweeted that there “ain’t enough money in the world to keep overlooking” the true issues affecting players and their families.

For weeks this summer, the NFL Players Association negotiated with team owners to figure out a return-to-work situation amid the COVID-19 crisis. It has been a borderline-rousing success so far, with the number of confirmed positive COVID tests dropping rapidly in recent days. Testing will cost the NFL $75 million this year, so this is a testament to what players can do when they stick together and what the league can do when it uses its financial might to get things done.

So what if players stuck together in a similar vein, and said they don’t feel comfortable playing given everything happening in America right now?

Is it unreasonable to think the threat of a walkout could lead to another negotiation between players and the league, one where players secure real, tangible help from ownership to tackle the issues that matter so much to so many of them before they even think about entertaining the masses?

There’s reason to be skeptical. The NBA is a far more progressive league. While the NBA has embraced players using the league’s platform for social justice causes, there’s no shortage of NFL team owners still trying to prevent their employees from kneeling during the anthem (see Jerry Jones’ recent comments). There are far more players in the NFL than there are in the NBA, and thus, more players that have to be on board with the idea for a walkout to have any weight.

Yet, there are signs of significant movement. The Detroit Lions, as a team, canceled practice Tuesday and used their platform to discuss the weekend shooting of Blake. Meanwhile, players and coaches across the league have been more outspoken on these issues than ever. Supporting social justice causes against police brutality and racial inequalities have become a safer play politically, one that a stone-cold business like the NFL might be apt to adopt to ensure the games (and thus, the cash) continue to roll in.

What any of this will look like, or whether it even materializes, is uncertain. But the Bucks’ historic decision Wednesday will have NFL players thinking about what they can do to send a similar message. If players settle on a similar protest, and players threaten to skip games or practices or whatever, Goodell had better have their backs, regardless of whether his 32 team-owning bosses agree.

Otherwise, he’ll show that he didn’t learn anything since Kaepernick first started taking a knee four years ago despite his recent proclamations to the contrary.

More from Yahoo Sports:

• NBA: Milwaukee stages walkout of Game 5 after Blake shooting

• Doc Rivers on Blake shooting: ‘This country doesn’t love us back’

• Lions cancel practice after Kenosha, send message on social injustice

• George admits he’s been dealing with anxiety, depression in bubble