When the No. 16 USC Trojans take the field for one of their most important games of the season against the No. 3 Ohio State Buckeyes at the Los Angeles Memorial Coliseum on Halloween night, one of the major questions is who they'll face at quarterback.

After the injury update that Buckeyes quarterback Julian Sayin will be out indefinitely, the competition for the starting position has begun between Luke Fahey and Tavien St. Clair. The Buckeyes have time to decide, as they are currently on a bye week following their 19-15 road win over the No. 6 Indiana Hoosiers in Bloomington.

Fahey starting for the Buckeyes against the Trojans on Oct. 31 would be a storyline in itself, as he's a former three-star recruit from Mission Viejo, California, which is on the border of the Los Angeles metropolitan area. St. Clair also has a strong case to start, as he's a former five-star recruit from Bellefontaine, Ohio.

Sayin’s injury impacts the Big Ten title and College Football Playoff race, and one conference team could benefit from the loss. That team is the No. 16 USC Trojans, whom the Buckeyes will face at the Los Angeles Memorial Coliseum after their bye week.

Depending on Saturday's road result against the Wisconsin Badgers at Camp Randall Stadium, a win over the Buckeyes will boost the Trojans' Big Ten title and CFP chances in their fifth season under coach Lincoln Riley.

How Julian Sayin's Affects USC Trojans

The Trojans (6-1 overall, 3-1 Big Ten) look to beat the Buckeyes without Sayin and give Riley his biggest win at USC. Facing the Buckeyes without Sayin gives the Trojans an advantage, and falling short at home against an Ohio State team without its leading signal caller would be a huge missed opportunity for Riley’s team. 

Despite Sayin’s absence, several Buckeyes on the roster will challenge the Trojans' defense, which has seen its fair share of ups and downs in its first season under defensive coordinator Gary Patterson. 

How Ohio State Can Still Beat USC Without Sayin

The country's best wide receiver and Heisman Trophy frontrunner, Jeremiah Smith, is one of those players looking to lead the Buckeyes to a win over the Trojans without Sayin. The Buckeyes star, with a backup quarterback under center, will look to make key plays against a struggling Trojans secondary. 

In seven games this season, Smith has recorded 52 receptions for 984 yards and 12 touchdowns. Smith is second in the country in receiving behind Oregon State Beavers wide receiver Jesse Legree, who has recorded 46 receptions for 1,040 yards and 14 touchdowns. 

The Trojans' defensive line, led by true freshman Luke Wafle, Jide Abasiri, and Jahkeem Stewart, has been the strongest unit on USC’s defense this season and looks to have success against the Buckeyes' running back trio of Bo Jackson, Ja’Kobi Jackson, and Isaiah West. 

Jackson leads the Buckeyes in rushing this season with 107 carries for 516 yards and four touchdowns. While the Trojans' defensive line has been dominant this season, there have been a few games where opposing teams have been able to find success. 

One of those games was the Trojans' 42-35 road win over the Rutgers Scarlet Knights on Sept. 19, when running back Antwan Raymond rushed for 122 yards and a touchdown. Ohio State running back Bo Jackson looks to replicate that success on the road. 

The Trojans and Buckeyes are scheduled to kick off in primetime on Halloween night at 4:30 p.m. PT, with the game broadcast on NBC. It’ll be the Trojans' fifth consecutive game in primetime on NBC, a streak that started on Sept. 26 with their 41-27 home loss to the Oregon Ducks at the Coliseum.