ORLANDO, Fla. -- For No. 15 UCF to ultimately get where it wanted to go, it had to get past nemesis South Florida, the team it had replaced as the favorite in the American Athletic Conference.

It took every last second to do that.

The in-state rivals played an incredible back-and-forth that ultimately came down to the final series, because that was the only appropriate ending to Friday night's showcase.

Let's just take the fourth quarter as our sample. USF entered with the lead. UCF then scored consecutive touchdowns to take an eight-point lead. Then, USF came right back and tied the game with a 2-point conversion.

Spectrum Stadium alternated between rollicking and literally shaking because of its jumping fans to utterly despondent after the Bulls tied it up. But one play sent the stadium back into hysteria -- Mike Hughes returned the ensuing kickoff 95 yards for a touchdown to allow the Knights to beat USF 49-42, stay undefeated and clinch a spot in the ACC championship game.

UCF plays Memphis next weekend in Orlando in a rematch of a Sept. 30 game the Knights won 40-13.

Folks in Orlando can breathe now.

There were plenty of Knights who impressed in their performance against USF, especially with their poise when trailing and when the Bulls tied them late.

If you consider everything else surrounding this team, the poise is even more impressive.

This is a team that has not only had to fight off inspired opponents in recent weeks, it has had to fight off plenty of distractions. Head coach Scott Frost has had his name come up on the coaching carousel for weeks, and again Friday, when sources told ESPN.com that Florida officials were scheduled to meet with his representatives this weekend.

The Knights' performance has been the subject of wild debate, too, after the College Football Playoff selection committee had the Knights behind three-loss Mississippi State and seven two-loss teams in the College Football Playoff rankings released earlier this week. Commissioner Mike Aresco was so upset, he said, "I just don't think our league is garnering the respect it deserves, period. I feel strongly about it. The evidence is in."

That might be true, but the only option UCF has to make its case is to continue to win. No matter where UCF ends up ranked, it'll clinch the Group of 5's spot in the New Year's Six bowls if it remains undefeated. Though the ranking is dispiriting, that should not take away from the season UCF has had.

This is the first time in school history the Knights have completed an undefeated regular season. And they clinched it with a performance for the ages.

For the majority of their game, the Knights showcased what got them to 10-0 -- a varied offense behind McKenzie Milton that moved easily between tempo, spread and option, with speed to spare.

But USF brought its own tempo attack, and Quinton Flowers helped the Bulls match the Knights score for score. Indeed, Flowers caused more problems for UCF than any quarterback had this season and finished the game with 605 total yards of offense -- 503 passing and 102 rushing.

Through three quarters, Flowers had 459 yards and four touchdowns, a big reason why the Bulls had taken the lead into the fourth. And he is the reason USF was able to tie the game with 1:41 remaining on an 83-yard touchdown pass to Darnell Salomon and then a 2-yard conversion to D'Ernest Johnson.

But special teams has been an Achilles' heel all season for USF, and UCF took advantage with a kickoff return that won't soon be forgotten.