The crumpled facemask served as a coach's memento, a reminder of a play that set Soma Vainuku on a path to the Senior Bowl.
In USC's 2012 opener against Hawaii, the Trojans scored a touchdown on their first snap and then kicked off, setting the stage for a raw redshirt freshman fullback to make his mark.
As the 6-foot, 250-pound Vainuku sprinted down the field in the Coliseum, a would-be blocker hit him and bounced away as if in a cartoon.
"It was almost like the guy ran into a brick wall," USC special teams coach John Baxter said.
Vainuku kept going and plowed into the kick returner, forcing a fumble that Hawaii recovered, before running to the sideline to find Baxter.
"How did I do?" Vainuku asked.
"You did good," Baxter said, realizing that Vainuku's facemask was bent into his mouth.
Baxter called for an equipment repair and kept the facemask in his office as a keepsake.
"I was like 'Holy smokes!" Baxter said. "This guy is a one-man wrecking ball.'"
Vainuku parlayed that debut into four years of standout special teams play for the Trojans. His performance, coupled with his speed and size, earned him a spot on the North team roster for Saturday's Senior Bowl, which is preceded by a weeklong evaluation in front of pro scouts.
USC quarterback Cody Kessler, UCLA receiver Jordan Payton and UCLA kicker Ka'imi Fairbairn also are on the North roster.
Vainuku arrived Sunday and in two days went through interviews with representatives from eight NFL teams.
Over three days of practices that begin Tuesday, Vainuku said that he wants to demonstrate his versatility as a blocker, ball carrier and receiver as a fullback, as well as the special-teams skills that could make him worthy of draft consideration.
"I just want to show my stuff," he said during an interview last week.
Fullbacks, once integral, are a vanishing breed in college football and the NFL. Vainuku and Northwestern's Dan Vitale are the only fullbacks among the 110 players on Senior Bowl rosters.
Last season, Vainuku carried the ball twice, once for a touchdown. He caught 17 passes at USC, none last season, and scored four touchdowns. Vitale, playing the so-called "superback" position last season, had no carries but caught 33 passes, four for touchdowns.
The Tennessee Titans selected Alabama's Jalston Fowler in the fourth round, the Detroit Lions took Rutgers' Michael Burton in the fifth, the Green Bay Packers selected Oklahoma's Aaron Ripkowski in the sixth and the Tampa Bay Buccaneers drafted Hawaii's Joey Iosefa in the seventh. The Buccaneers waived Iosefa, who signed with the New England Patriots.
Fowler, Burton and Ripkowski had limited roles on offense but all three played in nearly every game on special teams. Iosefa played in two games for the Patriots.
Gil Brandt was a Dallas Cowboys executive in the 1960s, '70s and '80s, during the heyday of fullbacks such as Robert Newhouse and Walt Garrison. Brandt noted that NFL teams today often use tight ends as H-backs for blocking out of the backfield and sometimes install linemen to pave the way for running backs in goal-line situations.
"The days of the blocking fullback are a thing of the past," said Brandt, a longtime draft analyst, "but everybody is looking for special teams players."
Vainuku said he learned everything about special teams from Baxter, who was not retained when Steve Sarkisian was hired as USC's coach before the 2014 season. Baxter worked last season at Michigan but has rejoined the Trojans staff under Clay Helton.
"I was sold before even getting recruited," he said.
Vainuku graduated early from Eureka High and said he was "an open book" when he enrolled with Kessler in January 2011. Former coach Lane Kiffin asked if he wanted to play linebacker or fullback.
"It didn't really matter to me," he said. "I told him fullback."
Vainuku redshirted in 2011 but did not lack for attention from Baxter, who often invoked his name.
"I spent most of that first year hollering at him," Baxter said. "I'd be yelling 'Soma!' Guys would imitate it."
Vainuku "morphed" into a special teams standout knowledgeable in every phase, Baxter said. In 2013, he blocked three punts and was voted first-team All-Pac-12 by conference coaches.
"Nothing else is better than blocking a kick," Vainuku said. "To me, it's more rewarding than scoring a touchdown."
Vainuku never complained to USC coaches about playing time or lack of opportunity on offense and never asked to switch to defense. His enthusiasm for special teams work allowed them to deploy Vainuku on nearly every unit, aiding a roster thinned by NCAA sanctions in his first few seasons.
"Whether it was zero plays or 20 snaps," he said, "my job was to make sure I was available to be there and be the guy they could count on."
Now he's in the Senior Bowl.
Vainuku said he plans to impart a message to scouts during interviews, practices and the game.
"I'm willing to get in there and work my butt off to show them that if they draft me," he said, "their number is not wasted."