He didn't, and that turned out to be a good move for the 21st-ranked Aggies.
With his team ahead 48-46, Quayle hit a long jumper, then stole the ball on the next play and drove for a layup to put Utah State in command and the Aggies beat Idaho 62-53 on Thursday night to extend the nation's longest winning streak to 19 games.
"I kept asking my assistants if we needed to take him out," Morrill said of Quayle, who finished with 12 points. "My assistants kept saying no."
Gary Wilkinson had 18 points and 10 rebounds for Utah State (24-1, 12-0), which clinched at least a share of its second consecutive Western Athletic Conference title.
Mac Hopson scored 17 points to lead Idaho (10-13, 4-6), which was done in by poor rebounding as it sought to beat a ranked opponent for the first time since 1982.
After Idaho tied it at 44 on Marvin Jefferson's basket with just over six minutes left, Stavon Williams' 3-pointer gave the Aggies the lead for good.
Quayle made his consecutive baskets to give Utah State a 52-46 lead with four minutes left. But Luciano de Souza replied with his third 3-pointer for Idaho.
Wilkinson's 3-pointer with just under two minutes left gave Utah State a 55-49 lead, and the Vandals were forced to foul.
Idaho is coached by Don Verlin, in his first season after spending the past decade as an assistant to Morrill at Utah State.
"Both teams had a pretty good idea what the other was doing, imagine that?" Morrill joked.
That familiarity made baskets hard to come by, he said.
Utah State, which leads the nation in field-goal percentage at 50.6, shot 40 percent. Idaho shot 36 percent in losing its ninth in a row to Utah State.
Hopson said the similarities were uncanny.
"You could tell by the way we warm up and they warm up," Hopson said. "It was identical."
Verlin said he thought his team played its best game of the season.
"When it was time to make a big shot tonight, they made it," Verlin said of Utah State.
Utah State dominated the rebounding, 40-21, and converted those into 20 second-chance points.
"If we play that hard the rest of the year, the wins will come," said Verlin, who already had Idaho off to its best start in a decade.
Utah State led 24-22 after a first half in which both teams had shooting woes. Then both teams started making shots, but could not separate.
The Aggies tied their team record of 19 consecutive wins, set in 1999-2000, and are tied with Oklahoma for most wins in the nation. Utah State has won 16 consecutive WAC games dating to last season.
Utah State's only loss was to Brigham Young on Dec. 6.
Morrill said the Aggies continue to find ways to grind out wins late in games.
"We found a way down the stretch," he said. "It's a 'W.'"