Miami and Oklahoma City, the last two undefeated teams in the NBA this season, both lost for the first time on Monday as the reigning champion Dallas Mavericks and Atlanta Hawks celebrated triumphs.
The Mavericks defeated the visiting Thunder 100-87, improving to 2-4 and avenging a loss at Oklahoma City last week, while the hosts Heat fell 100-92 to the Hawks despite a game-high 28 points from Miami's LeBron James.
Miami and Oklahoma City still share the NBA's best record at 5-1 after nine days of a season that was shortened to 66 games per club by a contract dispute between players and team owners.
At Dallas, German star Dirk Nowitzki scored 26 points and grabbed six rebounds to power the Mavericks while Shawn Marion added 17 points, Jason Terry added 15 and Vince Carter contributed 14.
Jason Kidd had a game-high nine assists for Dallas and Ian Mahinmi had a game-high nine rebounds for the Mavericks.
Reigning NBA scoring champion Kevin Durant led the Thunder with 27 points while Russell Westbrook added 18 points and eight rebounds.
At Miami, Joe Johnson scored 21 points and Al Horford added 16 points and nine rebounds to power the Hawks, who improved to 4-1, just behind Miami in the Southeast division.
Tracy McGrady added 16 points, seven rebounds and four assists for Atlanta.
Behind James, the Heat were led by Chris Bosh with 19 points and Dwyane Wade with 12 points and a game-high 10 assists.