They had spent the rest of it over the previous 40 minutes.
Hield scored 39 points, the second-most in Big 12 tournament history, while Niang had 31 in a dramatic quarterfinal duel Thursday night. But it was Hield and the sixth-ranked Sooners who managed to hang on through a tense closing stretch, emerging with a 79-76 victory inside the riotous Sprint Center.
"Two outstanding players," Sooners coach Lon Kruger said afterward. "He and Buddy respect each other so much because they always leave it out there. It was two really good players going nose-to-nose."
They weren't the only ones, either.
Ryan Spangler had 10 points and 12 rebounds, making a series of critical plays down the stretch, and Isaiah Cousins also had 10 points for the third-seeded Sooners (24-6), who advanced to play ninth-ranked West Virginia on Friday night in the semifinals.
But the spotlight shined most brightly on Hield, the league's player of the year, and Niang, who proved just as worthy while matching his career-high in his final Big 12 tournament game.
"It was fun competing against him," Hield said. "He's such a good competitor. He's a tough matchup to guard. He uses his body so well. Going against guys like Niang is fun."
More fun when you're on the winning side.
"From a friendship standpoint, I'm happy to say he's my friend and I'm proud of him," Niang said, "but from a competitive standpoint, I wish he would have missed a couple more shots."
As usual, Iowa State fans packed inside the Sprint Center, making their annual pilgrimage south on Interstate 35 in cars plastered in bumper stickers, flags and every other manner of Cyclones paraphernalia.
They seemed to give their boys a spark in the opening minutes, too.
The game eventually settled into a back-and-forth affair between teams that spent all season firmly entrenched in the Top 25. And it wasn't until Hield got going midway through the half that the Sooners created the slightest bit of separation, taking a 35-29 advantage into the break.
It grew quickly in the opening minutes of the second half, and a crucial series of plays near the midway point appeared to give Oklahoma enough breathing room to feel comfortable.
They began when the Cyclones' Nader was called for charging and Cyclones coach Steve Prohm went ballistic, drawing a quick technical foul. Hield made both foul shots. Then, when the Sooners set up offense, Cousins threw a lob that Hield dunked while getting fouled, and he made that free throw, too.
The five-point trip gave the Sooners a 55-42 lead with just over 10 minutes remaining.
Iowa State countered with seven quick points a few minutes later, and Niang proceeded to keep Iowa State in the game. The wily senior at one point scored 12 consecutive points for the Cyclones, including a couple of 3-pointers that even had Oklahoma fans expressing their appreciation.
Niang converted a three-point play to get the Cyclones within 72-66, then Nader buried a 3-pointer from in front of his own bench to make it 73-69 with just over a minute to go.
The Cyclones elected to play defense rather than foul, and it paid off when they forced Hield into an air-balled 3-pointer and a shot-clock violation. But with an open look from the corner at the other end, Nader misfired on a 3 that would have made it a one-point game and Spangler corralled the rebound.
The senior calmly made both foul shots to help seal the win.
"It was a game that could have gone either way," Kruger said. "We got a little bit of a margin in the second half. Proud of our guys for finishing it out."
The Cyclone's Monte Morris, an All-Big 12 performer, was limited to five points and two assists while dealing with a sore shoulder. He was just 1 for 9 from the field. "I'll give him a day to get away and get rested up," Prohm said. "We need him at full strength to be at the highest level."
Iowa State: Niang had 25 of his 31 points in the second half. It was the most scored by a Cyclones player in the Big 12 tournament since Jake Anderson had 33 against Colorado in 2011. ... Iowa State had won its last six games in the tournament.
Oklahoma: Hield was 14 of 21 from the field and 9 for 9 from the foul line. He also had nine rebounds. ... The tournament scoring record is 43 points, set by Texas Tech's Mike Singletary against Texas A&M in 2009. ... The Sooners have not won the tournament since winning three straight from 2001-03.
Iowa State awaits its NCAA tournament seed on Sunday.
Oklahoma plays West Virginia in the semifinals Friday night.