BOISE — This went way beyond just survive and advance.

This ventured into an absolutely uncomfortable area of frazzled nerves, bricked free throws and a heavy underdog poised to mess up a ton of brackets, particularly those in the Inland Northwest.

Just when it appeared plucky 13th-seeded UNC Greensboro was going to spring a huge upset, Zach Norvell Jr. remembered he’s Zach Norvell Jr.

Gonzaga’s redshirt freshman wing shook off a rough shooting night as he has done so many times this season, burying a 3-pointer that pushed the fourth-seeded Zags past the Spartans 68-64 Thursday at Taco Bell Arena.

Norvell’s 3-pointer — he was 1 of 7 from distance to that point — gave Gonzaga a 67-64 lead with 20.8 seconds left.

“Just toughness, having the courage and confidence to do it,” said Norvell, who made a slight adjustment to create space for the shot. “The entire game they were getting over ball screens pretty hard and hedging, I knew if I gave a little jab it would free me up.”

Did he know it was going in when it left his hand? Teammate Corey Kispert standing nearby heard the question and nudged Norvell, “Don’t lie.”

Only then did Norvell hesitate, taking a split second before saying, “Yes, every shot, other than a couple, felt really good.”

Most of the second half had an ominous feel for the Zags (31-4), who advance to face fifth-seeded Ohio State in Saturday’s second round. The Buckeyes outlasted South Dakota State 81-73.

“I’m up here shaking, still sweating,” Perkins said of the madcap finish. “I’m just glad I’m up here with this group of guys.”

Gonzaga couldn’t get away from the Spartans, even after building a 12-point lead early in the second half and a nine-point edge with 8:54 remaining.

The Zags rarely turned the ball over against UNCG’s 1-2-2 press, but they still didn’t find many easy buckets. They seemed to settle in, nailing 11 of their first 18 second-half shots, before going cold from the perimeter.

Senior forward Johnathan Williams, who finished with 19 points and 13 rebounds, and Perkins, who had 16 points, were the only reliable weapons for a majority of the contest.

“Their press helped them a lot because it slowed down our tempo,” guard Silas Melson said. “We like to get up and down and we weren’t able to do that pretty much for the entirety of the game.”

UNCG (27-8), known for its 3-point attack, missed all 13 long-distance attempts in the first half. The Spartans had a bit more success in the second half (3 of 9), but they seized momentum when guards Francis Alonso and Demetrius Troy punished the Zags with dribble penetration and artistic floaters, runners and flip shots.

“We get 22 (3-point) looks, I’d venture to guess 18 were pretty good looks for us,” Spartans coach Wes Miller said. “But I do think they were really extending on us and it allowed our guys to get downhill. We thought we could drive it.”

Each basket in the lane inspired more belief in the Spartans and turned some impartial fans among a pro-GU crowd into UNCG backers. UNCG mixed in a half-court zone defense that bugged the Zags, who couldn’t convert beyond the 3-point arc.

Troy’s twisting bank shot over Killian Tillie pulled the Spartans even at 62 and Jordy Kuiper’s tip-in gave them a two-point lead, their first since it was 13-12 midway through the first half.

Perkins made the game’s second-biggest shot, an 18-foot jumper that squared it at 64 with 53 seconds remaining. Norvell followed with the biggest shot of the season so far and it was nearly matched by UNCG forward Marvin Smith’s 3-point attempt that rattled in and out.

After a pair of missed free throws by Rui Hachimura — the Zags were just 13 of 25 at the stripe — Norvell hit 1 of 2 to seal the victory.

Gonzaga finally corralled Alonso, who scored 11 of his 16 points in the second half, in the closing 40 seconds. The junior guard forced a shot that was way off target and was called for a foul for pushing Melson.

“We just hung with it, hung with it,” GU coach Mark Few said. “We made one more play than they did. We’re fortunate to advance.”