The North Carolina freshman, already renowned for his ability to hit big late-game shots, knocked down a straight-away 3-pointer with 3.1 seconds remaining to give the 13th-ranked Tar Heels a 72-70 win against Florida State.
That shot--as well as the 11th double-double of the season from John Henson--kept alive Carolina's chances of winning the ACC title outright in the regular-season finale against Duke.
"I told them in the timeout that we were going to make the shot," UNC coach Roy Williams said.
That's the kind of confidence Barnes, who scored 18 points, inspires in the final seconds.
It's the second time in a row that the Tar Heels (23-6, 13-2 in the ACC) have won here at the Tucker Center on a last-second 3-pointer.
Last time, it was former UNC point guard Ty Lawson racing the length of the floor for a buzzer-beating three in 2009.
In that situation, the speedy Lawson was the only player Carolina could have expected to be able to make the play he did.
In this one, the same could be said for Barnes, who continues to amaze teammates and coaches with his ability to make crucial baskets in the waning moments of games--and then calmly discuss it like business as usual.
"It's very exciting to take the last-second shot and have the ball in your hands," Barnes said. "You're either the hero or the goat."
So far this season, Barnes has been the former every time.
He had already hit go-ahead or game-winning shots in wins against Virginia Tech, Miami and Clemson (twice) before sinking the Seminoles (20-9, 10-5).
"The type of player he is, you expect him to make it," Dexter Strickland said. "If he missed, you'd be surprised."
Barnes bailed out the Tar Heels, who panicked away a seven-point lead in the final three minutes, culminating in a pair of Derwin Kitchen free throws gave FSU a 1-point lead with 18.2 seconds to go.
That was the next to last of 14 lead changes in the game.
Up by three, point guard Kendall Marshall was trapped in the corner and turned the ball over instead of calling timeout. The result was a bucket for Kitchen.
Then Strickland made a wild drive to the basket and turned the ball over with 35 seconds to go, eventually leading to Kitchen's go-ahead free throws.
"The game of basketball is really crazy," Williams said. "We were in great position to have the game in our control, and we made about three of the dumbest plays you could ever make, and they're in control of the game."
Carolina was playing its first game since dropping down to eight healthy scholarship players, following the season-ending knee injury for freshman Reggie Bullock.
While Leslie McDonald chipped in 10 points off the bench thanks to three 3-pointers, the Tar Heels relied heavily on the starters, including a season-high 35 minutes from Henson
The sophomore tied a career high with 19 points and had 12 rebounds to bolster the shortened rotation.
Most impressive perhaps was that he was 5 for 6 at the free-throw line, meaning Williams was able to rely on Henson to be in the game in the final minutes when he might have to shoot free throws.
"John's a big defensive presence for us," Barnes said. "It's big for us to have him in the game."
In the final minutes, having Henson was a comfort, but Barnes was the one who saved the day.
The play the Tar Heels ran was one designed to have the ball in the point guard's hands but with one wrinkle: Williams swapped Barnes and Marshall.
Because Marshall wasn't spaced well in the unfamiliar wing spot, Barnes had no lane to drive if he wanted to.
That left him with only one option-to shoot the jumper over Michael Snaer.
In turn, that left the Tar Heels breathing another Barnes-born sigh of relief.
"He did a move that he does every day (in practice)," Henson said. "I saw it going in, saw the arc. He just hit the shot. We escaped."