Multiple NFL teams cancelled their Thursday practices in response to the police shooting of Jacob Blake in Kenosha, Wisconsin.
The New York Jets, Green Bay Packers, Indianapolis Colts, Tennessee Titans, Arizona Cardinals, Washington Football Team and Los Angeles Chargers were among those not to take to the field.
It comes amid widespread protests in the Unites States following the shooting of Blake, who was repeatedly shot in the back by police on Sunday.
His father said he has been left paralysed from the waist down.
Washington were the first to cancel practice, their decision coming shortly after the Milwaukee Bucks boycotted Game 5 of their first-round NBA Eastern Conference series against the Orlando Magic.
All of Wednesday and Thursday's NBA playoff games were postponed.
The Cardinals were among those to cancel their practice entirely, with head coach Kliff Kingsbury later addressing the media to explain the decision.
"What happened to Jacob Blake was horrendous and it has to stop," he said.
"I know it sounds hollow at times because you hear the same things over and over, but we wanted to make sure our players know that we support them and we're here for them.
"There's time where football takes a backburner and we felt like this was one of those moments as an organisation.
"We wanted our players to know that we support them and want them to have a day to be with their families, be able to reflect on things, be around friends, be around each other and then use the day to help make that change the way to see.
"Whether it's on social media, using that platform that they have, or if it's going to register to vote or trying to get other people set up to register to vote, we just wanted them to know this is their day and I felt like it was important to our organisation."
Cardinals running back Kenyan Drake wrote on Twitter: "We have the day off today to educate and reflect on who we are as individuals and here we need to progress as people.
"I'm honoured to be in an organisation of men and women who lead the charge for change in this country."
Jets running back Le'Veon Bell appeared to send a message to the NFL when he wrote: "We've been protecting the shield. It's time for the shield to protect us."
New Orleans Saints players did take to the field, with each player wearing a helmet with Blake's name written on it.
The Pittsburgh Steelers also practiced, and quarterback Ben Roethlisberger told reporters: "Everyone has the choice to choose to what level and what degree they want to use their platform.
"I think the biggest thing right now is to listen to my African-American team-mates and friends that aren't even in football just to get a better understanding to educate myself."