All three NBA playoff games at Walt Disney World Resort on Wednesday were postponed amid protests following the shooting of Blake – a black man who was repeatedly shot in the back by police.
It came after the Milwaukee Bucks – the top seeds in the Eastern Conference – decided to boycott Game 5 of their first-round postseason series against the Orlando Magic.
And in baseball, the Brewers followed suit after agreeing not to play their midweek fixture against the Reds at Miller Park in Milwaukee amid protests against racial injustice in the United States.
"The players from the Brewers and Reds have decided to not play tonight's baseball game," a statement from both sets of players said.
"With our community and our nation in such pain, we wanted to draw as much attention to the issues that really matter, especially racial injustice and systemic oppression."
The Seattle Mariners will also sit out MLB action midweek after players agreed to postpone their meeting with the San Diego Padres.
"The Seattle Mariners respect the team's decision not to play tonight's game," a statement read. "The Seattle Mariners stand with our players as they speak out with their words and actions against social injustice."
Mariners second baseman Dee Gordon wrote via Twitter: "There are serious issues in this country. For me, and for many of my teammates, the injustices, violence, death and systemic racism is deeply personal.
"This is impacting not only my community, but very directly my family and friends. Our team voted unanimously not to play tonight.
"Instead of watching us, we hope people will focus on the things more important than sports that are happening."
In a forceful message, athletes and teams downed tools in North America as they boycotted scheduled fixtures following the shooting of Jacob Blake, a black man, by police in the state of Wisconsin.
Blake was shot several times in the back, prompting nationwide protests.
All three NBA playoff games set for Wednesday were postponed, and it was reported widely that players from the Los Angeles Clippers and the Los Angeles Lakers were in favour of boycotting the rest of the season.
The NBA board of governors were set for a Thursday meeting, with players also reportedly due to hold a follow-up to their Wednesday get-together.
Major League Baseball saw three games postponed, namely those between the Milwaukee Brewers and Cincinnati Reds, Los Angeles Dodgers and San Francisco Giants, and Seattle Mariners and San Diego Padres.
Five of six Major League Soccer games also did not go ahead, while Thursday's play at the Western and Southern Open tennis tournament in New York was suspended, with Naomi Osaka pulling out of the tournament after reaching the semi-finals.
Former US president Obama saluted the Milwaukee Bucks for boycotting Game 5 in their series against the Orlando Magic.
Milwaukee is the nearest major city to Kenosha, where Blake was shot. Obama also saluted Clippers coach Doc Rivers, who criticised President Donald Trump when he spoke powerfully on Tuesday. Rivers accused the Republican Party of "spewing this fear".
Obama wrote on Twitter: "I commend the players on the @Bucks for standing up for what they believe in, coaches like @DocRivers, and the @NBA and @WNBA for setting an example. It's going to take all our institutions to stand up for our values."
Speaking earlier in the day, Lakers superstar James wrote on Twitter: "F*** THIS MAN!!!! WE DEMAND CHANGE. SICK OF IT".
Clippers owner Steve Ballmer added: "I am again angry over the shooting of a black man #JacobBlake. @DocRivers and The @Bucks players said it well, we need real police accountability. Give citizens data to do so. Let's have criminal justice reform that keeps all people safe but not senselessly imprisoned or afraid."
Tennis great King, who has fought for the growth of women's sport and for social justice, praised Japanese player Osaka's decision to abandon the Western and Southern Open in her individual protest.
King wrote: "A brave and impactful move by @naomiosaka, in support of the protest movement moving through the sports world. She was to play in the semis. Athletes using platforms for good means so much. Don't remain silent. #BlackLivesMatter"
Fellow tennis Hall of Famer Martina Navratilova added: "An amazing stance Naomi... well done, nothing but respect!!!"
The NHL faced criticism, however, for a perceived lack of response as the Stanley Cup playoffs continue.
Canadian star Evander Kane, who plays for the San Jose Sharks, tore into the league by saying: "Actually it's incredibly insulting as a black man in hockey the lack of action and acknowledgement from the @nhl, just straight up insulting."
