It’s Lincoln Riley’s Last Stand, and USC football fans don’t need to chug the contents of multiple beer swords to make a case for the Trojans holding firm.

Among the many theories as to why they could upset second-ranked Ohio State:

The Buckeyes will start either a true freshman or a redshirt freshman at quarterback after Julian Sayin suffered a severe shoulder injury.

The game is at the Coliseum, where Riley has gone 26-6.

Ohio State is favored by just 6.5 points, meaning even Las Vegas thinks the Trojans have a decent chance.

Then again, maybe a few cold ones might be in order given the counterpoints.

It doesn’t really matter who plays quarterback for Ohio State given the presence of wide receiver Jeremiah Smith, who turns 50-50 balls into something closer to 90-10 in his favor.

Buckeyes coach Ryan Day is a road winner, having notched 30 victories on the road since the start of the 2019 season to tie for the most in the country.

Ohio State’s defense is giving up 13.4 points per game, putting an extra onus on the Trojans’ defense to be equally stout.

Which way will the most pivotal game of Riley’s career go? 

Here are five things to watch when the Trojans (6-2 overall, 3-2 Big Ten) face the Buckeyes (6-1, 4-0) in a game that kicks off at 4:30 p.m. PT on NBC:

Crossroads for Lincoln Riley

A win over the Buckeyes would rally the Riley supporters, who could claim that he’s still the right man for the job and that the Trojans are back in the running for the College Football Playoff.

A loss would likely erode all remaining support.

With three losses, USC would be eliminated from CFP contention with three games left — including two against top-10 teams.

That might be the tipping point for those on the fence about paying Riley’s massive buyout in what’s supposed to be a make-or-break season.

Decision time

Day was cagey this week when asked about his quarterback situation, refusing to name a starter.

One option is Luke Fahey, a true freshman who played against Indiana after Sayin went down — and threw only two passes as the Buckeyes protected a late lead.

The other is Tavien St. Clair, a redshirt freshman who has appeared in two games, completing 5 of 7 passes for 52 yards with one touchdown and one interception.

“They’re going to have a new guy back there,” Riley said, “and we’ve got to make life really tough on him.”

No matter who is the starter, expect plenty of passes to be thrown to Smith, the Heisman Trophy candidate who needs only 246 receiving yards to break the Big Ten career record.

More Jayden Maiava magic?

For the season’s first few weeks, the Trojans thought they had their own Heisman candidate in Jayden Maiava.

But the veteran quarterback has fallen off his prolific pace while struggling with his decision-making under pressure.

Last week, during the Trojans’ loss to Wisconsin, he was sacked five times and tallied more interceptions (2) than touchdown passes (1) for the first time this season. He also failed to see open receivers on multiple plays.

“Just didn’t play to my standard and the Trojan standard,” Maiava said. “Got to play better.”

Run game shakeup

USC mostly relied on King Miller and freshman Shahn Alston in its run game last week, with Waymond Jordan not getting a carry for the first time all season.

Riley said Jordan and fellow running back Riley Wormley — who also didn’t get a carry — were both available but held out of the rotation because of coach’s decisions.

Alston was the most productive rusher against the Badgers, rushing for 28 yards in seven carries, but nobody ran for more than 7 yards on any play and the team’s minus-17 yards rushing total was largely a function of so many sacks.

That can’t happen again against the Buckeyes.

“We need to create some explosive runs,” Riley said. “I mean, that takes so much pressure off the other parts of your offense.”

Injury report

USC tight end Mark Bowman, who was a big contributor in the season’s early going, remains questionable for a fourth consecutive week.

Trojans defensive tackle Jahkeem Stewart was also listed as questionable, along with Alston.

Ohio State wide receiver Brandon Inniss, who has made 11 catches for 153 yards and one touchdown this season, is listed as questionable.