We all know by now that Stafon Johnson is most likely done for the rest of the season.

He was involved in a tragic accident that no one could have predicted or prevented.

But what we don’t know is how the USC offense will respond to the incident. More specifically, how will this impact the rotation of running backs on the roster?

Four games into the season, the senior Johnson had established himself as USC’s premiere goal-line back. He led the team with five rushing touchdowns and was second on the team with 157 rush yards, an average of 4.9 yards per carry.

He scored the most touchdowns because coach Pete Carroll trusted Johnson with the ball in the red zone and gave the senior more opportunities than any other running back to score when the Trojans were near the end zone.

That trust is now gone. And even Carroll isn’t sure who will be getting the ball in those situations this Saturday against California.

“We’re working on it,” the coach said in a press conference on Tuesday. “We’ll see what we’re going to do about that.”

Unlike many teams, USC has the luxury of many highly recruited running backs on its roster that could possibly fill the void left by Johnson. There is a list of possible scenarios that could play out when No. 7 USC visits No. 24 Cal this weekend.

Option One: The Joe McKnight Show.

McKnight already leads the team in rush attempts at 47 and rush yards at 362. But the junior is definitely the type of talent that has a chance to produce some gaudy numbers if he takes more handoffs from freshman Matt Barkley.

Without Johnson, McKnight may get the opportunity to take control in the backfield. Although McKnight leads the team in rush attempts, he has only been given the ball to run on 32 percent of USC’s running plays.

That number could now bump up to 35 or even 40 percent if Carroll decides to keep McKnight on the field more because of Johnson’s injury.

Is that too many carries for McKnight to handle?

No.

Cal’s stud running back Jahvid Best has carried the ball 69 times this season and has accounted for 44 percent of the Bears’ running plays.

The question is whether or not Carroll will trust the ball in McKnight’s hands on the five-yard line.

One of McKnight’s biggest weaknesses throughout his time at USC has been ball security. And the last time a coach wants to see his team cough the ball away is when it’s about to push it in the end zone for six.

Option Two: There Once Was A Man Named Gable.

Remember him?

Back in 2006 as a freshman, C.J. Gable ran 111 times, second on the team to then-redshirt junior Chauncey Washington’s 157 attempts, and gained 434 rush yards, third best on the team. He also scored four touchdowns.

After an injury-plagued 2007 season, Gable returned last season to rush for 617 yards on 107 attempts and scored eight touchdowns — the second highest on the team and only one behind Johnson.

But in 2009, Gable has played in three of the Trojans’ first four games and rushed for just 44 yards on only 10 attempts.

Gable said he was ready to go in the Trojans’ loss to Washington two weeks ago and expressed frustration after not getting any playing time after Trojan running backs continued to fumble the ball away. Carroll, however, said Gable had not recovered from the flu and was not available.

“I want to get in, but I’ve got to wait until whenever my time is,” the running back said following the game.

Maybe now is the time.

Gable ran only three times for two yards against Washington State last Saturday, but without Johnson’s services, Carroll may look back down memory lane.

At 6 feet, 205 pounds, Gable represents a bigger option than McKnight if Carroll wants to pound the ball into the end zone. Carroll also said during Monday’s practice that he would heavily consider giving Gable more opportunities to run from this point forward.

Option Three: Spread The Wealth.

Instead of giving more carries to McKnight or Gable, Carroll can decide to spread the carries out until someone emerges as a solid goal-line running back.

That means guys like redshirt junior fullback Stanley Havili, redshirt sophomore tailback Marc Tyler and redshirt junior tailback Allen Bradford will get more chances to show what they can do on the field, especially near the end zone.

Out of that mix, I’d give Bradford the advantage. He’s a bulky running back at 5-foot-11, 235 pounds, and he can move when the ball is in his hands. He also has the best build to pound the ball for short yardage gains — which would be very beneficial near the end zone.

So Carroll clearly has some options to consider when putting together his game plan this weekend. Although we won’t know what he chooses until game time, one thing is clear.

Without Johnson, the Trojans’ backfield is a bit less crowded, but a lot more complicated.

“Soft Hands” runs every other Thursday. To comment on this article, visit dailytrojan.com or email Jon at jhaber@usc.edu.