The Tigers (10-19, 3-12 Southeastern Conference) rallied from a 20-point first-half deficit and survived a wild final sequence when the teams swapped turnovers in a 2-second span. It was the second-biggest margin Auburn has overcome to win, trailing only a 22-point rally against Louisville in 1995.
Ole Miss (18-12, 6-9) had a couple of chances for the go-ahead basket in the final seconds before Nelson's 3-point attempt from behind halfcourt hit off the backboard at the buzzer.
The Rebels' full-court press forced a turnover with 16 seconds left after Chris Warren's 3-pointer cut Auburn's lead to 74-73. They gave it right back when Warren lost the ball out of bounds.
Ole Miss then forced a bad pass by Earnest Ross that Nelson picked off. He passed inside to Nick Williams, who couldn't control the ball.
It went back to Auburn and Denson for two more free throws with 2.1 seconds left.
The Rebels had won the first meeting 90-59 on Feb. 16 and threatened to run away with this one early, too.
The Tigers then opened the second half on a 16-5 run, including Gabriel's 11 points.
Gabriel scored 15 points in the second half for Auburn, which was coming off back-to-back two-point defeats in a four-game skid.
Ross added 15 points, while Chubb and Denson had 11 apiece. Chubb scored six straight points in a 90-second sequence to push Auburn's lead to four points with 1:33 left. All of his points came in the second half.
The Tigers made 9 of 10 free throws in the final 1:33 to keep the Rebels from overtaking them. They were 31 of 40 from the line in the game.
Warren, the SEC's No. 2 scorer, scored 10 points but was 3-of-16 shooting and made just one of his 10 3-point attempts -- though that was the big one late.
Terrance Henry had 13 points, but he and Warren were among four Ole Miss players who fouled out.
Auburn took a 72-67 lead, matching its biggest of the game, with 1:03 left on Gabriel's two free throws. He was fouled after grabbing the rebound when Tony Neysmith missed his second attempt from the line after making the first.
But Warren was fouled attempting a 3-pointer five seconds later, and the nation's leading free throw shooter hit all three from the line. Denson hit two more free throws for Auburn but Warren answered with a second-chance 3-pointer with 21 seconds left to cut it to 74-73.
That's when they traded turnovers, and Ole Miss couldn't get another shot off until Nelson's last-gasp try.
Nelson had helped the Rebels surge to a 41-25 halftime lead. He had 19 points and six 3-pointers in the half, making his first five. The 5-foot-11 freshman, who was making his third start, hadn't scored more than 17 points or hit more than three 3-pointers coming into the game.
He made his first five 3s this time.
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