LOS ANGELES (AP) Oregon's spread offense can challenge the discipline of even the most experienced defender through its use of motion and formations.

''In the last game, even though they only had 49 plays I think there was 22 or 23 different formations,'' said Southern California defensive coordinator Justin Wilcox, referencing the Ducks' 38-36 win at Stanford.

In other words, there may not have been a worse possible time for the No. 22 Trojans (7-3, 5-2 Pac-12) to have lost their starting inside linebackers, breakout freshman Cameron Smith and reliable redshirt senior Lamar Dawson, to season-ending injuries.

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USC is experimenting in practice with different pairings to replace Dawson and Smith, the team's leading tackler. Redshirt senior Anthony Sarao worked with sophomore Olajuwon Tucker and converted outside linebacker Uchenna Nwosu, while Tucker and freshman Osa Masina also played together. Michael Hutchings, a junior, could be in the mix as well.

Interim coach Clay Helton said the plan is to use four inside linebackers against No. 23 Oregon (7-3, 5-2) on Saturday, but who and in what combinations would not be decided until later in the week.

''It is just part of this game and we're excited about those guys getting an opportunity to play some more snaps,'' Wilcox said.

Tucker looks to be the likely candidate to replace Smith, who tore a knee ligament in the first half against the Buffaloes last week, but played another 18 snaps after suffering the injury.

''What a warrior,'' Helton said. ''He went until he couldn't go anymore.''

A four-star recruit who played at Serra High in Gardena, California, alongside USC sophomore cornerback/wide receiver Adoree Jackson, Tucker has mostly been limited to special teams and mop-up duty in his first two seasons, with 12 career tackles in 10 appearances.

After not appearing in the previous five games, Tucker was able to get some valuable playing time against Colorado. He finished with four tackles, working next to Smith as a weak-side linebacker after Dawson went down with a shoulder injury before taking Smith's place in the middle after he finally yielded to his injury.

Tucker was upbeat coming off that performance, saying it reinforced the mindset necessary to perform at a high level.

''No nerves around here. We prep for this,'' Tucker said. ''I think (Wilcox and linebackers coach Peter Sirmon) did a good job getting me into the mix this week and my confidence is up.''

Whether that will translate into the eye discipline needed to see through Oregon's clutter is another matter.

The Ducks had five plays of at least 30 yards against the stout Cardinal, including touchdowns of 75, 47 and 49 yards. USC's defense has not allowed a scoring play of more than 9 yards during its last three wins, and Wilcox understands that not allowing explosive plays is the key to stopping Oregon.

''There are going to be times where they can get a number advantage,'' Wilcox said. ''Whether it is at defensive line, whether it is at linebacker, whether it is in the secondary, you are going to have to win some one-on-ones and get off a block and everybody run to the ball and make a tackle.''