When it counted, Ray Allen does what he signed up for

MIAMI — The Miami Heat were less than six seconds away from entering NBA history as a Big Three disappointment following a 66-win regular season.

A feeling of White Hot desperation filled AmericanAirlines Arena late Tuesday night as Ray Allen took a pass from Chris Bosh in the far right corner.

Despite a 1-for-5 shooting effort to that point, Allen did what he was signed to do last summer — what he had done all those years in Boston, including in 2008 when the Celtics won the title.

Allen added to his NBA record of career playoff 3-pointers, tying the score at 95 with 5.2 seconds left and sending an already thrilling Game 6 against the San Antonio Spurs into overtime.

Miami went on to prevail 103-100 to force a Game 7 on Thursday night that will decide this season’s champion.

“It’s going to be a shot I remember for a long time,” Allen said. “There’s a lot of shots that I’ve made in my career, but this will go high up in the ranks because of the situation.”

With 19.4 seconds remaining in regulation, San Antonio’s Boris Diaw replaced Tim Duncan. The veteran Spurs center appeared to have turned back the clock, scoring 25 first-half points, but Duncan managed just five in the second half.

“It’s what we’ve done all year,” Duncan said of being replaced. “We got a stop, and we got a bad bounce, and right out to Ray Allen for a 3. Just situational.”

After Kawhi Leonard hit one of two free throws with 19.4 seconds remaining, the Heat came down the floor trailing 95-92. LeBron James put up a 3-pointer that missed its mark, and Bosh grabbed the rebound in the paint.

Already facing Allen’s direction, Bosh threw the ball to No. 34 despite James calling for it with both arms raised at the top of the key.

“If it’s not me taking the shot, I have no problem with Ray taking that shot, man,” James said. “He’s got ice water in his veins.

“Ray can be 0 for 99 in a game, and if he can get an open look late in the game, it’s going down.”

Bosh hadn’t noticed Duncan not battling for the rebound and didn’t see James begging for the ball.

“I can’t tell you who was on the floor besides Ray,” Bosh said.

Allen had backpedaled to behind the 3-point line once he saw James’ shot miss.

“I was hoping I was where I needed to be, but I wasn’t quite sure,” he said. “But just from years of shooting, I got to my spot.”

Because he did, Allen is 48 minutes away from achieving what he hoped after turning down Boston’s two-year, $12 million offer last July. He joined Miami’s Big 3 of James-Dwyane Wade-Bosh as an outside threat who would help the Heat repeat as NBA champions.

“When I parted ways with Boston, it was … they went in their direction, and I obviously went in mine,” he said. “The minute I got here, this team made me feel welcome. I didn’t win last year with this team, but they made me feel part of it.”

Allen sank 11 of 17 from beyond the arc through the first five games of the series and missed his first two shots from long distance in Game 6.

Then …

“Ray did what he’s done for so many years,” Heat coach Erik Spoelstra said, “and we’ve seen it on the other side many times.”

Charlie McCarthy can be reached at mac1763@bellsouth.net or on Twitter @mccarthy_chas