SALT LAKE CITY -- 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 on Thursday.

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.

Oregon 68, Oklahoma State 55

SAN JOSE -- The Oregon Ducks picked up right where they left off in the Pacific-12 Conference tournament last weekend, parlaying a stingy defense with dominance on the backboards to a stun stunning victory in the Midwest Regional second round at HP Pavilion.

The Ducks, who earned just a No. 12 seed in the region despite having tied for second in the Pac-12 regular season before sweeping to the conference tournament title, advance to a third-round matchup Saturday in San Jose against fourth-seeded Saint Louis, a 64-44 winner over New Mexico State earlier in the day.

Iranian-born senior forward Arsalan Kazemi recorded an 11-point, 17-rebound double-double, helping the Ducks (27-8) to a 44-32 board advantage and a 12-6 margin in second-chance points against the fifth-seeded Cowboys.

Marquette 59, Davidson 58

LEXINGTON, Ky. -- Vander Blue hit a running lay-up with one second left completing Marquette's comeback win in a second-round game of the East Regional at Rupp Arena.

Davidson's De'Mon Brooks threw the ball away with 6.7 seconds left and a one-point lead, and Marquette was given a final shot. Jamil Wilson inbounded the ball to Blue near midcourt with five seconds remaining, and Blue drove all the way to the basket on Davidson's Jake Cohen.

Blue, a 6-foot-4 guard, went to his left and got the ball off the backboard just over Cohen, who is 6-10.

Davidson (26-8) had won 17 games in a row, which was the longest active winning streak in the country.

Blue hit a 3-pointer with 28 seconds left to bring Marquette within two points, but Nik Cochran answered with two free throws for the Wildcats.

Memphis 54, St. Mary's 52