TUCSON, Ariz. — Tyler Huntley was down on a sack, but it didn’t look all that serious.

Then it did.

Then it was as serious as a sermon.

The Ute training staff was accompanying its starting quarterback to the locker room, with 8:45 left in the first half of Friday’s Pac-12 opener between Utah and Arizona. Everyone knew something like this could happen at some point, but so soon? Huntley doesn’t have a low gear. He’s out there, all the way, all the time. But in this case, it wasn’t necessarily his fault. It was a sack.

Still, the first night of conference play? That’s just cruel. It’s Fate flexing its muscles. Welcome to college football. It’s a business with all sorts of variables. BYU lost starting quarterback Tanner Mangum earlier this month. Huntley, with star quality in every move, was gone. Troy Williams — last year’s starter — was in.

This, then, is where the Utes will be tested. The first unit is swift and talented, picked to finish second in the Pac-12 South. But in today’s world, it’s not always the first team that decides the season, but everyone else. That’s how you find out how far your program has progressed: When a team can take the hits.

Starting defensive end Kylie Fitts was helped off the field limping late in the first half. He didn’t start the second half.

Fitts missed all but two games last year due to a season-ending injury.

For a few minutes, the future looked fair to partly cloudy for the Utes, despite the departure of Huntley. Williams immediately completed a 40-yard pass. Soon came a touchdown toss — though it was later ruled incomplete. The Utes settled for a field goal to lead 13-3 with 5:39 left in the half.

Utah has never hidden the fact it worried about Huntley. From the first game, coach Kyle Whittingham and staff have admitted the possibility of injury was real. But a sack is a bad way to go. Huntley wasn’t roaming unchecked in the open field. He was doing his job.

After leaving, Huntley sat on the bench in dejection for a few minutes with a towel draped over his head, then walked unaided up the tunnel.

With him went the momentum Utah had in the first half. The Utes clung to a 13-10 lead at the midway point.

So Williams was back in the saddle. He was not happy when he lost his starting spot before the season started. He didn’t outright criticize coaches, but he made sure everyone knew he felt he had earned the position.

It’s likely he’ll get plenty of chances to prove himself again this year.

Whittingham loves to use the phrase “next man up.”

That’s a hackneyed phrase, but it was apropos Friday.

The Utah-Arizona series has some history, as well as intrigue. In some ways, they’re companion schools. Both left what originally was the WAC, with dreams of playing in the Rose Bowl. But neither has been there. They and Colorado are the only Pac-12 teams never to do so.

A USA Today report showed that in 2015-16, Arizona’s athletic revenue was 39th nationally, Utah’s 45th. Despite Utah’s No. 21 national ranking in the coaches’ poll, in some ways Friday’s game was a match of equals.

Arizona came in having won four of six games against the Utes since 2011. In that time, the Wildcats got a division title, but overall they had just a 21-33 conference mark and, going into Friday’s game, were 4-14 in conference games the last two seasons. Utah was 25-29.

Utah started the second half the way it ended the first — with Williams at quarterback. Noting changing. But safety Chase Hansen was back for the game, nabbing an interception in the third quarter.

Meanwhile, Williams got his old spot back — under circumstances he never wanted. But Utah wasn’t a diverse or particularly productive offensive team last season. In the first half on Friday, Williams was 4 for 7 for 48 yards passing. But 40 of those came on one play.

Utah started the second half looking a lot like it did last year — getting its yards via ground delivery, Zack Moss and Devonta’e Henry-Cole doing the early work. But Williams completed a 37-yard pass to Demari Simpkins with 10:18 left in the third quarter. Soon the Utes were in the end zone, for a 20-10 lead.

Ups and downs.

That’s the how it goes in college football.

“Next man up” might end up the last man standing.