The protests, which were also carried out in the WNBA and impacted some games in Major League Baseball and Major League Soccer, were spurred by the police shooting Sunday of a Black man, Jacob Blake, in Kenosha, Wisconsin.
The first team to boycott a game was the Milwaukee Bucks, who were scheduled to play the Orlando Magic in a playoff game at 4:30 p.m. ET in the NBA's Orlando bubble. All three games on the NBA schedule were eventually postponed.
Milwaukee is about 40 miles north of Kenosha.
"We support the fight against racism and injustice," Boston Bruins captain Zdeno Chara said after a 7-1 loss to the Tampa Bay Lightning in Game 3 of the Eastern Conference Second Round. "There are different ways to express that fight and obviously NBA players expressed their opinions by boycotting the games today. We support it."
The NHL played three games on Wednesday, a 3 p.m. ET game between the New York Islanders and Philadelphia Flyers, an 8 p.m. ET game between the Bruins and Lightning, each played in the Eastern Conference hub city of Toronto, and a 10:30 p.m. ET game between the Colorado Avalanche and Dallas Stars, played in the Western Conference hub city of Edmonton.
Players on the Bruins and Lightning said that they found out about the boycotts as they were getting on the bus and heading to the rink, at which point it was too close to game time for the discussions that would have needed to take place.
"I think, personally, with our team, we played last night, we played today, the other leagues hadn't taken their stances until we got here tonight," Lightning defenseman Kevin Shattenkirk said. "I think for us it was something we found out when we got to the rink and something we have to address going forward."
Stars forward Tyler Seguin, who along with teammate Jason Dickinson knelt for the United States and Canada national anthems before a game Aug. 3, said boycotting a game is not the only way to show your support for the cause.
"I think there are different ways to show your actions and what you support, [Dickinson] and I did our first game," Seguin said after Dallas' 6-4 loss to the Avalanche in Game 3 of the Western Conference Second Round. "I fully support what the NBA and MLB are doing, and we had the decision tonight to play the game. We look forward to showing our actions more in the coming days."
Avalanche center Nazem Kadri agreed.
"It crosses your mind when you see other leagues doing something like that," Kadri said. "We support and applaud the NBA for taking those circumstances. I understand, this is a problem that has gone on for far too long. The signs, the hockey ops is great and everything but, you know, eventually words get stale and it's about action and making a difference."
Video: Lightning, Bruins hold moment of reflection
There was a moment of remembrance before the Lightning-Bruins game in which Blake was mentioned.
Former NHL forward Anson Carter, now an analyst for NBC Sports, said he didn't have an issue with the NHL playing its games Wednesday.
"I'd be okay with NHL players playing. I would look at my guys around the room and say, 'I'm okay with us playing.' But I understand the Bucks, I understand the (Milwaukee) Brewers because that's close proximity to where Kenosha is, so I understand the relationship they have with those communities." said Carter, who is Black. "But when it comes to NHL players, I'm okay with them not protesting, I'm OK with them playing the game, continuing to play. And also, the League went about their business and identified and acknowledged what has happened.
"But my focus right now really is, what are we doing about it? Yes, we can protest. Yes, we can sit out. But what change are we actually trying to do? If you protest and go about your business and nothing really changes, then what is the sense of protesting? The focus really should be now on, what are we doing to change? So the focus really should be now on what are we going to do to change? Like in Atlanta where I live, State Farm Arena now has been opened up as a polling center because voter suppression is real in the south. That something that we could see NHL owners or NBA owners doing to try to" make things happen."
Matt Dumba of the Minnesota Wild, a member of the Hockey Diversity Alliance who gave a speech about anti-racism before a game between the Edmonton Oilers and Chicago Blackhawks on Aug. 1 and knelt for the U.S. national anthem, called the decision to play by his fellow players "disheartening" on a Vancouver radio station Wednesday.
The speech was referenced by Lightning coach Jon Cooper, when he was asked about Dumba's comments.
"Being part of a professional league, I watch so many good things all professional leagues do," Cooper said. "I look around at our arena and I sit back and think about when we first got here and the emotional speech that Matt gave that was so moving and that guys still talk about what's gone on and what's happened.
"Unfortunately, we can't control some of the things that go on in the outside world. I truly believe whether it's pro sports or the business world or whatever it is, at some point we're going to have to come together. Whether you say the NHL is behind or ahead, the League has done so many good things in so many different avenues, this is one we need to pick our head up, and there's no doubt we will."
Cooper was asked on Thursday morning if playing the game on Wednesday was the right thing to do.
"I don't think anything feels right right now. So much education that needs to go on. I know that the players, they battle hard on the ice, they compete against each other, they also stand together too." Cooper said. "As an organization, as a League - I don't know how to say it - these events are happening and I think it's time to digest. It's hard for me to answer right now. I said last night one night of sleep is not enough to digest. I know since communicating with our team and being open with what's going on, I think that's a good step for us moving forward and we'll see what happens here."
Islanders coach Barry Trotz said his players were discussing the situation ahead of their game against the Flyers on Thursday.
"They understand the importance of the playoffs, but they also understand where the world is right now and what happened yesterday," Trotz said. "We weren't really quite informed what was happening; we were playing when all this happened, and then as you get to digest it, I think what happened last night is a great statement for the athletes. They have a great platform, and they used it.
"I just heard that the NBA is going to continue to play, and in my opinion, I think all the sports should play because I think the athletes in every sport have a great platform, just like celebrities do. If you want to keep the issue in the forefront, these athletes have a great platform. So continue to play, continue to express the message, and then the next step is what's the end game? We've got to know the definite end game. And then, I think you have to get involved. The players are going to have to get involved, I'm going to have to get involved. Everybody. If you do that, that will effect change for our country, and it definitely needs it right now."
NHL.com staff writers Brian Compton, Tracey Myers and David Satriano contributed to this report