Inter Miami, with superstar Lionel Messi still resting after his World Cup exploits, won 1-0 at Montreal on Saturday on Casemiro's Major League Soccer debut.
Luis Suarez converted a penalty in the 81st minute to secure the victory after Miami's Mexico international German Berterame was injured in a sickening clash of heads.
Berterame crashed to the turf and lay motionless after Efrain Morales made contact as they jumped for the ball.
Players from both teams immediately signalled for help and, after treatment by medics and a long delay, Bertrame was taken from the pitch in an ambulance.
Miami coach Guillermo Hoyos said later that Berterame was "OK and conscious".
"His family has been informed of everything. We didn't know what to do – it was a very desperate situation."
Suarez converted the ensuing penalty and held up Berterame's jersey to mark the goal.
The Uruguayan former Liverpool and Barcelona forward extended his scoring streak to six goals in his last three matches, taking his total for the season to nine.
Casemiro, who has 91 caps for Brazil and won five Champions League titles with Real Madrid, made his first appearance for Miami since arriving this week from Manchester United.
The 34-year-old controlled the tempo in midfield throughout the match, but both teams struggled with poor finishing.
Messi and his Argentina teammate Rodrigo De Paul both missed a second straight game in the wake of Argentina's defeat to Spain in the World Cup final last weekend.
MLS officials said Saturday that Messi would not be required to play in next week's All-Star game.
Miami have won both their matches since MLS resumed after the World Cup, taking their win streak to six and leaving them two points behind Eastern Conference leaders Nashville, who lost 1-0 at Orlando City.
Chicago Fire, beaten by Miami on Wednesday, lost 3-1 to New York City FC at Yankee Stadium to leave Robert Lewandowski still in search of a first victory since signing from Barcelona.
Agustin Ojeda, Nicolas Fernandez and Malachi Jones scored for New York with Joel Waterman on target for Chicago.