Kelly Olynyk scored 17 of his 21 points in the second half and Kevin Pangos hit a late clutch 3-pointer to help No. 1 seed Gonzaga survive a scare from 16th-seeded Southern with a 64-58 victory.
Pangos finished with 16 points, including a dagger of a 3-pointer that gave Gonzaga a 62-58 lead with 1:57 remaining. Pangos then helped the Zags avoid being the first No. 1-seeded team to lose to a No. 16 squad by hitting two free throws with 14 seconds remaining.
Southern (23-10) had to remind Gonzaga (32-2) of its old self by nearly pulling off the huge upset in this first-round game.
Derick Beltran scored 21 points and played a key role in helping Southern go on a 12-2 run late in the second half. Yondarius Johnson got the comeback going, hitting a 3-pointer with 8:13 to go after Olynyk's strong second half put Gonzaga up 52-42.
Beltran then scored seven straight points before Brandon Moore tied it at 54-54 with 4:08 remaining with two free throws.
Gary Bell Jr. drained a 3-pointer to put the Zags up by three, but Gonzaga couldn't shake the SWAC champions.
Beltran got Southern back within one point after two free throws with 2:28 remaining before Pangos hit his key 3-pointer.
Malcolm Miller's 3-pointer rimmed out with 1:20 remaining for Southern, and the Zags escaped down the stretch to avoid the stunner.
Gonzaga will play No. 9 Wichita State on Saturday.
The game started like a normal No. 1 vs. No. 16 matchup.
The Zags scored the first seven points and looked to be en route to an expected rout.
But Southern had other things in mind.
Miller got the Jaguars on the board for the first time at the 16:12 mark with a 3-point bucket that sparked Southern's fuse.
Moore hit a jumper and Miller drained another deep shot to cap an 8-0 run that gave Southern its first lead of the game at 8-7.
Gonzaga re-established a slim advantage with a 7-0 spurt in the first half, going ahead 25-19 on an Olynyk layup.
But Moore, Beltran and Jameel Grace each hit 3-pointers in the first half and Southern only trailed 34-31 at halftime.
Olynyk had 17 of his points in the second half, pushing Gonzaga to its 10-point lead.
NOTES: David Stockton recalled getting in trouble as a rambunctious child inside the arena where his dad, John Stockton, played most of his career with the Utah Jazz. "We were Rollerblading here down a little spiral thing and I ran into a Coke machine and broke my collarbone," he said. "They had to get my dad out of practice. He was probably the most mad at me for that." ... Southern wasn't eligible for the NCAA Tournament last season because of a postseason ban. ... Stockton wasn't the only son of a former NBA player on the court. Southern's Madut Bol's father is the late Manute Bol.