The Cougars had 13 turnovers at half. At that stage of the game Iona's starters were on fire. Mike Glover made 5-for-8, Randy Dezouvre was 4-for-6, Lamont Jones 3-for-8, Machado 3-for-3 and Sean Armand 4-for-4.
Rose tried to get the Cougars to attack Iona with Davies and Hartsock but players on the floor failed to find a rhythm, panicked and got down quick.
But shuffling in freshmen DeMarcus Harrison and Anson Winder at key times with Craig Cusick taking over the point for freshman Matt Carlino, Rose saw his team whittle things back to a doable project in the final 10 minutes.
Iona looked spent, tired and unable to answer BYU's charge. It was as if their remarkable 55-point first half cost them everything they had in the tank and the Cougars were ready to pounce and eat.
BYU took its first lead of the game 71-70 at the 2:18 mark on a 3-point basket by Hartsock. The Cougars never looked back.
"I give BYU all the credit for the comeback they made," said Iona coach Tim Cluess.
"They made shots, they made plays. We had opportunities, but I think we were 1-for-15 on 3s in the second half. You're not going to beat anyone that way."
Cluess said his squad just couldn't make shots in crunch time.
"We've had a couple of these losses this year like that and it really stems from the fact that when we don't make shots, we're not the same type of team. We're a small team. They went inside, did a great job of getting it inside and kicking it back out.
"So I give them a lot of credit. We weren't good enough in the second half to withstand that comeback."
The Cougar now face No. 3 seed Marquette in Louisville on Thursday.
They're human, it will take time to get over this one.
- Big winner: Utes hit jackpot early and often...
- Brad Rock: This is where conference switch...
- Penn State sweeps BYU for a record seventh...
- Dick Harmon: Execution, not words, will crown...
- Tyler Haws scores 24 as BYU holds off Stanford
- Wyoming transfer Jason Thompson makes Utah...
- Utah State caps historic season with win over...
- Jennifer Hamson to lace it up for BYU one...
- BYU football: Cougars in talks with... 62
- BYU defensive back transferring to Utah... 51
- Hamson and Gray step up big to get BYU... 45
- Big winner: Utes hit jackpot early and... 42
- BYU sells close to 2,000 tickets for... 40
- Dick Harmon: How a simple decision in... 34
- Ute football team has boots on the... 33
- Ranking the biggest bowl games in... 28