Warning signs

The Trojans returned to their winning ways by routing previously ranked Oregon. Now comes the hard part: getting up for a struggling opponent. Times staff writer Gary Klein looks at some of the key issues and matchups when USC plays the Sun Devils, who have lost three consecutive games and have not defeated USC since 1999:

On the mend

The game was expected to feature the Pacific 10 Conference’s total offense leaders, Arizona State’s Rudy Carpenter and USC’s Mark Sanchez.

At least it did before they suffered injuries last week.

Sanchez is back, so the big question is whether Carpenter, the Pac-10’s most experienced quarterback, will play.

The senior from Westlake has started 36 consecutive games, but that streak is in jeopardy because of an ankle injury. Carpenter, who has passed for 1,337 yards and eight touchdowns with five interceptions, sat out two days of practice this week, worked with the second unit Thursday and is begging Coach Dennis Erickson to give him a final shot at the Trojans, who sacked him six times last Thanksgiving.

If Carpenter cannot play, junior Danny Sullivan will start.

Sanchez has recovered from a bone bruise in his left knee, suffered as a result of a sack by Pac-10 leader Nick Reed of Oregon. Sanchez has passed for at least three touchdowns in every game this season, so the Trojans better keep an eye on Arizona State defensive end Dexter Davis, who is second in the conference in sacks.

Carry on

USC’s tailback rotation is coming into focus, with sophomore C.J. Gable and junior Stafon Johnson trading carries and sophomore Joe McKnight getting touches mainly outside the tackles and as a receiver.

Gable is quietly averaging 6.1 yards a carry, McKnight 5.9 and Johnson 5.3.

The rushing attack has taken a back seat to the conference’s best passing game, but for a team averaging 38 points, it’s hard to believe that the Trojans have rushed for only four touchdowns in four games.

Arizona State is ranked last in the Pac-10 in rushing. If the offensive line cannot clear some room for running backs Keegan Herring or Dimitri Nance against the Trojans, who rank fourth nationally in total defense, Carpenter or Sullivan could be on the run – or the ground – all day.

Catching on

Receivers Patrick Turner, Damian Williams and Ronald Johnson are stretching the field for Sanchez and have combined for 10 touchdowns.

Johnson is averaging 25.5 yards a reception, Williams 15.5 and Turner 15.1. They will operate against a Sun Devils defense ranked sixth in the Pac-10 against the pass.

Carpenter or Sullivan will rely on receivers Michael Jones, Kyle Williams, Chris McGaha and Kerry Taylor, especially if the Sun Devils’ rushing attack provides no support.

Return engagement

Underdog Arizona State could use a big play or two from its special teams. USC needs to avoid mistakes that would give the Sun Devils advantageous field position.

Stafon Johnson takes over punt-return duties for the Trojans, replacing the fumble-prone McKnight. Johnson’s main mission is to catch and secure the ball, but the junior is fully capable of electrifying returns.

Arizona State’s Williams is averaging 14 yards a return.

Flag football

The Trojans are a four-touchdown favorite over Arizona State, which began the season with victories over Northern Arizona and Stanford before losing to Nevada Las Vegas, Georgia and California.

But USC could keep Arizona State in the game if it continues to amass nearly nine penalties a game, worst in the Pac-10. The Trojans average 86 penalty yards.

Arizona State is averaging 57.8 penalty yards.

By the numbers

 gary.klein@latimes.com