ATLANTA - J.R. Smith knocked down a tough 3-pointer, then another. Turning toward the fans, their heckling transformed to groans, he blew off his right index finger and motioned toward his side, like he was holstering his pistol.

Yep, Smith was that hot.

While LeBron James led Cleveland with 31 points, it was Smith who ignited the Cavaliers in Game 1 of the Eastern Conference finals. He made eight 3-pointers and scored 28 points in a 97-89 victory over the top-seeded Atlanta Hawks on Wednesday night.

"When he gets hot," Cleveland coach David Blatt marveled, "he gets smoking hot."

Intent on bringing Cleveland its first NBA title, James sealed the victory with a soaring dunk in the final minute.

For the Hawks, it was the second straight series in which they've lost the opening game at home. Cleveland will look to take command of the series in Game 2 Friday night.

Making matters worse for Atlanta, DeMarre Carroll went down with a knee injury driving to the basket with 4:59 remaining. He was helped to the locker room, not putting any weight on his left leg, and will undergo an MRI on Thursday to determine the seriousness.

Besides being the main defender on James, Carroll had been the Hawks' leading scorer in the playoffs. He was averaging more than 17 points coming into Atlanta's first conference final.

"DeMarre is a complete player," Hawks coach Mike Budenholzer said. "He has a big impact at both ends of the court."

Jeff Teague led Atlanta with 27 points. But Atlanta didn't produce its usual balanced scoring, as two starters — Kyle Korver and Carroll — failed to reach double figures.

With Smith doing most of the damage, Cleveland outscored the Hawks 22-4 over the final 5 minutes of the third quarter and the first 2 minutes of the fourth. During that span, he made five 3-pointers and another jumper from just inside the arc, as well as throwing up a lob that Tristan Thompson dunked.

Smith has been a huge addition for the Cavaliers since he was acquired in January as part of a three-team trade with New York and Oklahoma City. A player once known for his selfishness, he had learned to work with within the confines of a team led by James.

When the Cavaliers really needed Smith in Game 1, he seemed to make every shot.

"Once I start shooting," Smith said, "everybody keeps telling me to keep shooting."

Cleveland scored the first 11 points of the final period — all but two on 3s by Smith — for its biggest lead, 85-67.

Carroll's injury silenced the raucous crowd and would be a tough blow for the Hawks to overcome. While he was being taken off, James came over to say a few words and pat the injured player on the head.

"We're all a brotherhood," James said. "You don't want anybody to get hurt like that."

Even without Carroll, Atlanta closed to 91-87 with about a minute remaining. But James got loose from Paul Millsap out near the arc, took off down the lane uncontested and slammed home a dunk that finished off the Hawks.

Having made their deepest run in the playoffs since 1970, the Hawks carried that momentum to a nine-point lead in the opening quarter. Atlanta shot 61 per cent and James went to the bench with about 3 minutes remaining in the period after picking up his second foul.

Cleveland's dominance on the boards kept Atlanta from pulling away. Cleveland outrebounded the Hawks 15-6 over the first 12 minutes, actually yanking down more offensive rebounds (seven) than Atlanta's total output.

James returned in the second quarter and began to take control of the Cleveland offence. He scored 14 points in the period on 7-of-9 shooting, taking advantage when the Hawks tried to bait him into a third foul by guarding him with smaller players.

The game was tied 51-all at the half.

POUNDING THE BOARDS

The Cavaliers finished with a 49-37 rebounding edge, exposing Atlanta's major weakness during the regular season.

Timofey Mozgov led with 11 rebounds, while Thompson chipped in with 10.

James also had eight rebounds, giving the Cavaliers three players who had more than anyone on the Hawks. Millsap, Kyle Korver and Al Horford each had seven for Atlanta.

TIP-INS

Cavaliers: This was the first time in franchise history that Cleveland won Game 1 of a playoff series on the road. The Cavs had been 0-14. ... Thompson had 14 points, while Mozgov and Iman Shumpert added 10 apiece.

Hawks: Horford had 16 points, Millsap 13 and Kent Bazemore 10, including a massive dunk in the second half. ... Bazemore figures to get even more playing time if Carroll is sidelined. ... Floyd Mayweather Jr. was sitting courtside. When he was shown on the video board, most of the crowd booed.

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Follow Paul Newberry on Twitter at www.twitter.com/pnewberry1963