Posey hit a 3-pointer at the buzzer Saturday night to give the Heat a 98-97 win over the Memphis Grizzlies.
Trailing 97-95, Miami controlled a jump ball with 1.8 seconds left and called timeout to set up the final play. Jason Williams threw the ensuing inbounds pass to Posey on the left baseline, and he launched a shot from 26 feet over the outstretched arms of Mike Miller for the game-winner.
"J-Will made all the reads for the play, and when I got it, I had a good look," Posey said. "I got a great look. I could see the basket. The only thing I was really worried about was my feet being inbounds."
Officials reviewed the play before ruling it good both from outside the arc and before time ran out.
Miller, who lunged at Posey as he got off the shot, said there wasn't much more he could do.
"It's pretty self-explanatory really. He made a tough shot," Miller said. "I really don't even know if he looked at the winning shot."
Dwyane Wade led the Heat with 23 points, including 12 in the fourth.
Antoine Walker scored 18 points, while Williams added 13 points and 14 assists.
Miller had 22 to lead Memphis, while Rudy Gay added 20, including a pair of free throws in the final 22 seconds to give Memphis a 97-95 lead and set the stage for the last-second shot.
It made for a different ending than Miami's previous two setbacks, where the Heat lost by three points to Orlando and two points on Thursday against the Detroit Pistons.
"It was just a matter of time," Wade said. "You have to give these guys credit for sticking with it. When things looked bad, we still kept sticking with it. That kind of game can change a season."
Both teams were playing without their all-stars big men. Miami's Shaquille O'Neal is recovering from right knee injury, while the Grizzlies' Pau Gasol has not seen action this season, after off-season left foot surgery from an injury suffered in the world games.
Williams, who has been slowed by off-season knee surgery, was called on to play a season-high 38 minutes because of foul trouble for Wade. He was making only his third start of the season.
The Heat took a 57-48 halftime lead thanks to a hot-shooting first half. Midway through the second quarter, Miami held a 49-27 lead and was shooting 68 percent from the field. Williams had 13 assists out of Miami's first 19 field goals.
Hakim Warrick helped close the gap in the second quarter, as he scored 15 points in the first half.
"We gave ourselves a chance in the second half by minimizing turnovers, and we had a much better defensive effort," Memphis coach Mike Fratello said. "They were shooting over 60 percent in the first half, so to get it down to 51 percent at the end of the game, we must have done something good."
That defense contributed to the Heat hitting only 4-of-18 field goals in the final quarter, including Posey's game-winner.
"It just burns, period," Grizzlies guard Dahntay Jones said of the last-second loss.
- Saturday was Dorell Wright's 21st birthday. The Heat swingman, in his second year out of South Kent Prep, is the youngest player on the Miami roster. He started his fifth game of the season and finished with 14 points.
- Williams played in Memphis from 2001-2005. His 14 assists without a turnover was the best performance by a Miami player since Tim Hardaway had 13 assists without a turnover in 1997.
- Heat C Alonzo Mourning had seven blocks, a season-high for a Memphis opponent, including five rejections in the third quarter.
- Miami G Gary Payton did not play because of a left ear infection.
- Memphis G Dahntay Jones, who started for the first time this seas on, scored 12 points, marking his third consecutive game in double figures.