UCF: Darriel Mack

Central Florida quarterback Darriel Mack Jr. (8) celebrates after scoring the go ahead touchdown against Memphis during the second half of the American Athletic Conference championship NCAA college football game, Saturday, Dec. 1, 2018, in Orlando, Fla. (AP Photo/John Raoux)

When Central Florida quarterback McKenzie Milton was carted off the field with a gruesome knee injury in the Knights' regular-season finale against South Florida, it was a fair question to wonder whether UCF's shot at another major bowl game left with him.

A week later, UCF was down 31-14 to Memphis in the second quarter of the American Athletic Conference championship game — seemingly a half away from getting beat for the first time since 2016.

But then McKenzie's backup, Darriel Mack, led the Knights to a 56-41 comeback victory. The 6-foot-3, 230-pound redshirt freshman scored six touchdowns: He was 19-of-27 passing for 348 yards and two touchdowns, and he rushed for four more touchdowns, including the final three scores of the game.

Surrounded by reporters after winning the program's second consecutive AAC title, Mack said he'd just got off the phone with McKenzie, who said "he loves me; he's proud of me."

First-year coach Josh Heupel felt the same way about the player who likely saved the season for No. 8 UCF (12-0), which will play No. 11 LSU (9-3) in the Fiesta Bowl on Jan. 1.

"I thought (Mack) performed extremely well," said Heupel, who was the offensive coordinator at Missouri when he was hired to replace Scott Frost, who left UCF for Nebraska. "Everyone in our program has a lot of confidence in him. You can see that in the way we called the game. We were really aggressive and put the ball in his hands. Obviously, he took an opportunity and ran with it and played extremely well."

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The question now becomes how aggressively the UCF coaching staff will use Mack against LSU — the self-proclaimed "Defensive Back University" that will be without its two starting cornerbacks.

The Tigers will also have to play for a half without starting inside linebacker Jacob Phillips, who was ejected for targeting during the seven-overtime loss to Texas A&M in the season finale.

Left cornerback Kristian Fulton has been out since suffering an ankle injury Nov. 10 at Arkansas, for which he underwent surgery Friday. Right corner Greedy Williams announced Sunday on Twitter that he will enter the 2019 NFL Draft. An LSU official confirmed that Williams will not play in the Fiesta Bowl.

Freshman Micah Baskerville likely will play in place of Phillips at inside linebacker, as he did against Texas A&M, but it's uncertain how the LSU coaching staff will rotate its defensive backs to make up for those personnel gaps.

Head coach Ed Orgeron and his staff are on the road recruiting this week, and the team likely won't have media availability until they return. Orgeron phoned into Sunday's Fiesta Bowl media teleconference and was surprised when Williams made his announcement in the middle of the call.

It's still nearly a month until the Fiesta Bowl, and having just learned his opponent within a few hours, Orgeron couldn't comment too much on the game plan against Mack and the Knights.

"I watched a couple plays (on television Saturday)," Orgeron said. "Obviously, we were busy doing other things. I can't comment on it right now."

The secondary already has seen some shifting around the past few weeks:

• Stanford graduate transfer Terrence Alexander started in place of the injured Fulton in the final two games of the regular season against Rice and Texas A&M.

• Second-team corner Kelvin Joseph, a true freshman, returned from a hamstring injury he suffered against Arkansas to provide depth against Texas A&M. The 6-foot-1, 195-pound Scotlandville graduate is available to play against UCF.

• Starting nickel safety Kary Vincent played some corner against Arkansas and recorded a one-handed interception in the fourth quarter. Vincent stayed at nickel safety against Texas A&M.

The Tigers surrendered their second-fewest passing yards of the season (101) against Rice, which finished its season 2-11. Texas A&M quarterback Kellen Mond threw six touchdown passes, two of which were in regulation.

Heupel didn't comment on a game plan against LSU's defensive backs on Sunday, and he pointed out that it had been awhile since his last game against LSU. Missouri lost 42-7 to LSU in 2016 during Heupel's first season as offensive coordinator.

"They're going to be long and athletic," Heupel said of LSU's defensive backs. "They're going to run very well."