In a number of ways, it’s been a bit of a quiet spring for USC.

Senior quarterback Matt Barkley has taken fewer reps in order to allow redshirt freshmen signal callers Cody Kessler and Max Wittek to spend more time with the first team unit. Both are competing for the backup spot.

Junior All-American wide receiver Robert Woods, a preseason Biletnikoff Award candidate, has sat out of all 12 workouts while recovering from an offseason ankle surgery.

And in general, many of the eye-popping plays have been made by the defense.

In short, its spring practice and the highlight plays are typically few and far between, as is customary for many schools nationwide.

One of the bigger stories in recent weeks for USC has been the play of sophomore Tre Madden, a converted linebacker and special-teamer in 2011 who switched to running back to shore up a position that lacked depth.

This spring, the Trojans only have three scholarship tailbacks available — in addition to Madden — in redshirt freshman Javorious “Buck” Allen, senior Curtis McNeal and sophomore D.J. Morgan.

But on Thursday, things changed.

During the Trojans’ 11th spring-practice session, Madden attempted to plant his left foot, but instead fell to the ground — despite no contact.

Less than 24 hours later, Madden underwent X-rays, revealing a torn ligament that will require surgery and will force him to miss the entire 2012 season — a significant blow considering his strong play as of late.

“Probably one of the most valuable guys on our team,” USC coach Lane Kiffin said following Saturday’s scrimmage at the Coliseum. “We don’t have anyone like him. Nor do we have anybody coming in like him.”

The allure of Madden has always been his size. Listed at 220 pounds, he is roughly 30 pounds heavier than both McNeal and Morgan, who project to be atop the Trojans’ depth chart come the Sept. 1 opener against Hawai’i.

Madden tends to rely on strength, with a combination of speed; he has been clocked at running the 40-yard dash in 4.5 seconds.

In short, the former Mission Viejo High School standout is the big, bruising runner the Trojans have not quite found since LenDale White paired with Reggie Bush as the famed thunder and lightning duo in the mid-2000s.

Kiffin compared Madden to White at Saturday’s scrimmage, but “with longer speed and really good hands.” The comparison — though lofty — isn’t too far off.

“The sky was the limit and it will be when he comes back,” Kiffin said. “I think he will be a great player.”

Offensive coordinator and running back coach Kennedy Polamalu echoed a commonly held sentiment, at least among the coaching staff: Madden’s future is bright, still.

“In just my eyes and being around the position for 20-plus years, I think he would have been really special,” Polamalu said. “The nice thing is he has a redshirt and we’ll bring him back. People have come off the ACL [tear] and done well.”

Madden will stay at running back when he returns from the injury next spring. And considering McNeal is expected to graduate, that’s probably for the best. The position projects to be even thinner.

The Trojans are in need of depth, in part, because of scholarship restrictions preventing them from carrying more than 75 scholarship players.

Kiffin and company are still in search of that complementary back for this fall, and as the injuries pile up, so does the number of candidates.

Next in line? It appears to be Allen, the 6-foot, 215-pound redshirt freshman tailback from Tallahassee, Fla., along with incoming freshman wide receiver Nelson Agholor, who is expected to log carries at the position during fall camp.

At more than 200 pounds, Allen might eventually become the Trojans’ best bet at fulfilling that “big back” role for this season at least.

Returning from a hamstring injury, Allen’s first extended practice came during Saturday’s shortened scrimmage — speeded up, perhaps, because of Madden’s anterior cruciate ligament tear.

“I knew I had to help my team,” said Allen, who remarked that his hamstring was about 90 percent healed. “I knew I had to step up and make a move for my team.”

If Allen can fulfill that role, the Trojans would be more than welcome to factor him into the rotation in some capacity. After all, it’s an important one.

Granted, he hasn’t played much, battling injuries.

He redshirted last fall, as well — his first season with the program.

But the options are limited and finding that bruising runner is something of a necessity to some degree.

“You always want a finisher,” Polamalu said. “You want a guy at the end of the game. It’s nice to have that finisher so that the defense gets a break. So the quarterback gets the coverage he wants and that we need to see.”

Unfortunately for Polamalu and the rest of the staff, that search continues.

“The 19th Hole” runs Mondays. If you would like to comment on this story, visit DailyTrojan.com or email Joey at jrkaufma@usc.edu