Two-time defending NBA champions Miami have now dropped five of their last six games after a 111-107 loss to the Denver Nuggets.
Kenneth Faried registered a double-double, scoring 24 points and grabbing 10 rebounds to lead the Nuggets.
Down by four, forward LeBron James missed a three-pointer with 26.9 seconds remaining.
The current stretch matches the worst six-game run for the Heat since the start of the 2010-11 season and puts them three games back of Indiana for the Eastern Conference's No. 1 seed.
Raptors 99, Grizzlies 86
Jonas Valanciunas had a season-high 23 points as the Toronto Raptors defeated the Memphis Grizzlies 99-86.
Kyle Lowry had 22 points and 12 assists while Greivis Vasquez had 17 points off the bench for the Raptors.
The Raptors (37-27) used a late run to pull away for their 11th win in 14 games while snapping a four-game home losing streak against the Grizzlies.
DeMar DeRozan finished with 16 points.
Zach Randolph led the Grizzlies (38-27) with 16 points.
Trail Blazers 111, Pelicans 103
Damian Lillard scored 16 of his team-high 27 points in the fourth quarter to lift the Portland Trail Blazers to a 111-103 victory over the New Orleans Pelicans, snapping a four-game road losing streak.
With the Blazers down 94-89 with 7:26 left, Lillard scored 12 of his team's next 18 points in a 6:12 span to help Portland take a 107-100 lead.
Nick Batum added 22 points and Wesley Matthews added 20 for Portland (43-23).
The Pelicans (26-39) were led by Anthony Davis, who scored a career-high 36 points, his fifth consecutive game with at least 28.
Bobcats 105, Timberwolves 93
Al Jefferson put on another show with 25 points and 16 rebounds as the Charlotte Bobcats won their third straight, beating the Minnesota Timberwolves 105-93.
The Bobcats erupted for 65 first-half points and led by as many as 16 in the first half, then kept the lead in double figures the entire second half.
The win was the Bobcats' fifth in their last six games and moved them to 32-34.
For Jefferson, it marked the 20th time this season that he has had at least 20 points and 10 rebounds in a game, which established a franchise record.
The Timberwolves, who had won four of their previous five, fell to 32-32 with Kevin Martin providing 19 points.
Pacers 101, 76ers 94
The Indiana Pacers produced a 101-94 victory over the Philadelphia 76ers.
Paul George put on a show with 13 points in the third quarter on his way to 25.
David West scored 18 points, George Hill contributed 14 and Lance Stephenson had 13 points and 12 rebounds for the Pacers, who improved to 48-17 and won their second straight following a four-game losing streak.
The Pacers have the best record in the Eastern Conference.
The Sixers, who were within three late in the contest, were led by Thaddeus Young's 25 points and 10 assists before dropping to 15-50, a 19th straight loss.