Mississippi's Jason Holmes goes up for a rebound against Notre Dame's Ryan Humphrey.(AP)

With the shot clock winding down and only 46 seconds to go, Harrison pulled up and drained an unexpected 3-pointer that put the Rebels on top 57-55.

A moment earlier, Ryan Humphrey's basket had just given Notre Dame it's first lead of the second half between these two evenly matched squads.

"I looked at the shot clock and it had eight," Harrison said. "It's one of those shots you dream about. I knew I had to make a play. I hadn't made a play in a long time and I didn't want to let the team down."

The Rebels (27-7), whose victory total is a school record, will meet No. 2 seed Arizona Friday in the Midwest Regional semifinals in San Antonio. After being picked last in the SEC West, they have advanced farther than any Ole Miss team ever.

Mississippi coach Rod Barnes admitted a lot of college coaches wouldn't even have bothered to recruit Harrison.

"I don't mind taking a chance on somebody when they have great character," said Barnes. "Size is the most overrated thing in basketball."

With 22 seconds left, Emmanuel Wade hit a free throw for Ole Miss, then Matt Carroll answered with a foul shot for Notre Dame (20-10), which was gunning for its first regional appearance since 1987.

With 18 seconds left, Sanders missed the front end of a one-and-one, but was there to block Carroll's attempt at a game-tying 10-footer.

"We're a defensive team. That's what got us here," said Sanders. "We look for that last stop on defense. He shot it right into my hand. He was just trying to get a shot off with the clock running down."

Jason Flanigan's foul shot with two seconds to go iced it for the third-seeded Rebels, who held Notre Dame to 29 percent shooting.

"A lot of it was their defense," said Mike Brey, who capped his first year as Notre Dame coach by leading the Irish to their only NCAA appearance in 11 years.

"They made more plays at crunch time than we did," said Brey.

Troy Murphy, Notre Dame's two-time All-American forward, had 17 points but was just 1-of-7 in the second half.

"They made me catch the ball in spots where it was harder for me to score, about 20-22 feet out," Murphy said. "They did a heck of a job."

He was asked if he'll skip his senior season to enter the NBA.

"It's a tough way to end the season but it's been a great year. Coach and I will have to sit down some time and weigh the options and then make the decision based on that," he said.

Rahim Lockhart, Mississippi's muscular 6-8 center, scored his team's last eight points of the first half and totaled 24 points even though he kept coming out for brief rests in the second half.

With Notre Dame's defense sagging in on him every time he got the ball down low, Lockhart ended the game in obvious fatigue. No other Rebel had more than seven points.

"Coach put a lot of confidence in me today," he said. "They said they were going to come to me as much as possible."

The Rebels went on an 11-2 run beginning the second half, capped by Jason Holmes' 3-pointer and David Sanders' layup off an inbounds pass, and took their biggest lead, 39-31. Murphy stopped the spree with a 5-footer at the 16:33 mark.

Despite missing 36 of their first 50 shots, the Irish trailed only 47-40 when Murphy's two free throws triggered an 11-4 run capped by Humphrey's three-point play that tied it at 51 with 5:09 to go.