Less than 24 hours earlier, Barkley had been flat on his back on the rain-slicked Rose Bowl turf, a crunching hit from a Bruins linebacker injuring his right shoulder and forcing him to leave the stadium with his arm in a sling.
Now, with the senior's season and USC career possibly over, a somber Kiffin tried to console the player who passed up the chance to earn NFL millions and came back for a final campaign with the Trojans.
But it was Barkley who provided perspective.
"Remember Coach," Kiffin recalled Barkley saying, "this is a sport. This doesn't define who I am."
If there truly is some emotional pain there, Barkley is keeping it well hidden. And he's certainly not talking about it.
Barkley has not practiced for the Dec. 31 Sun Bowl against Georgia Tech, has not addressed the local media in weeks and has declined requests for one-on-one interviews.
"He doesn't want to be the focus right now," an athletic department spokesman said.
It's an unexpected but perhaps understandable turn for a 22-year-old who returned for a shot at winning a national championship and the Heisman Trophy but experienced a disappointing 7-5 regular-season finish instead.
Senior center Khaled Holmes, Barkley's teammate since high school at Santa Ana Mater Dei, said that behind closed doors the two team captains were at times "down in the dumps" about the way their final season was playing out. Barkley "maybe more so because of what he gave up to come back and the opportunities he had," Holmes said.
Barkley, though, remained positive in public and with teammates.
"But, you know," Holmes said, "he's human too."
Barkley's smile stretched the width of the giant Coliseum videoboard.
He had just established a Pac-12 Conference record for career touchdown passes, and now thunderous cheers from more than 80,000 fans rained down on him during the Trojans' Oct. 20 game against Colorado.
Barkley happily mugged for a sideline camera that projected his larger-than-life image to an adoring crowd.
It was the last time in 2012 that Barkley looked so joyous on a football field.
Ten months earlier — a year ago Saturday — Barkley had stood up in front of a giant, sparkly Christmas tree in Heritage Hall and announced during a nationally televised news conference that he would put off entering the NFL draft, citing "unfinished business" and hinting at glory awaiting a USC program emerging from some of the most severe NCAA sanctions in college sports history.
But shortly after the season began, things started to go awry.
In September, Stanford pummeled Barkley and surprised the No. 2 Trojans, putting a national championship and the Heisman in doubt. USC rebounded with four consecutive victories, but then lost four of its last five games, the shoulder injury forcing Barkley to sit out the regular-season finale against Notre Dame for the second time in three years.
The Heisman front-runner became a Heisman afterthought. His draft stock slipped.
Those who know Barkley best say his strong Christian faith and character prevent him from answering questions with anything but total honesty.
And Barkley remained candid this season — at least until the Trojans began their season-ending downward spiral with a late-October defeat at Arizona. As losses and his interception total mounted, Barkley seemed increasingly subdued, as if hesitant to speak his mind.
Early this month, he apparently could no longer hold it in. During a national radio and television interview on Dan Patrick's syndicated show, Barkley lauded Trojans receiver Marqise Lee, who supplanted Barkley as USC's Heisman candidate. And then, without prompting, he added that at times the Trojans focused too much on the sophomore and that "we could have done a better job of utilizing other players."
The comment hinted at Barkley's frustration over Kiffin's play-calling.
Kiffin rebutted the comment the next day, but he acknowledged last week that Barkley's season did not play out as planned.
"I don't think anybody could have ever pictured the season going the way it did," he said.
When former USC coach Pete Carroll bolted to the NFL in January 2010, Matt Barkley faced the media and assured teammates, fans and fence-sitting recruits that everything would be fine.
Five months later, the NCAA hammered the Trojans with a two-year bowl ban and other penalties for violations related to former Heisman Trophy winner Reggie Bush. It was Barkley who stood before reporters in Heritage Hall that day. His message: The Trojans will persevere.
Barkley certainly did.
Building on some of the successes from his freshman season — he led USC to a victory over Ohio State in front of a crowd of more than 106,000 in Ohio Stadium — Barkley steered the Trojans through their transition to Kiffin and an 8-5 finish.
In 2011, he broke out, passing for a conference-record 39 touchdowns , with only seven interceptions. He led the Trojans to an upset victory at Oregon and then a 50-0 rout of UCLA to finish 10-2.
And then, after placing sixth in Heisman balloting and pronouncing that he was more than ready to play in the NFL, he decided instead to complete what he started at USC.
Barkley's longevity helped him establish 20 USC records, 10 that double as conference marks.
But he will end his career without having been voted first-team All-America, or even first-team all-conference. He led the Trojans to the Emerald and Sun bowls, but did not play in the Rose Bowl game or any other BCS bowl.
Barkley has said repeatedly that he did not second-guess his decision to return for a final season.
"Whether it entered his mind, I don't know," Kiffin said. "But I never heard anything or saw any reactions that were like, 'Why did I stay?'"
Barkley's father, Les, said the season was frustrating for all Trojans players and their families. But his son does not look back.
"He's had an incredibly fulfilling experience at USC," Les Barkley said. "He doesn't regret it at all."
USC has not officially announced Matt Barkley's status for the Sun Bowl, but with February's NFL scouting combine and the pre-draft evaluation season approaching he almost certainly will sit out against Georgia Tech and avoid further injury.
Gil Brandt, a former Dallas Cowboys executive and a longtime NFL draft guru, dissected tape of every pass thrown by Barkley in 2011.
He watched him closely this season as well.
"He just didn't look like the same player that he was last year," Brandt said.
Barkley passed for 36 touchdowns, but also had 15 passes intercepted in 11 games, more than double his 12-game 2011 total.
Before the UCLA game, NFL scouts told The Times that Barkley rated high in experience, leadership skills and intangibles, but they questioned his arm strength on certain throws and also his mobility.
Several factors, however, could work in Barkley's favor.
And Barkley , a polished speaker with 47 college starts and no off-the-field baggage, is expected to shine in interviews with NFL team executives.
"This has happened before with quarterbacks," Brandt said. "We overvalue them and come back and undervalue them."
Barkley's draft fate will be determined over the next few months.
"We'll see," Brandt said, "when he works out at the combine."
How will Barkley be remembered at USC?
After watching him navigate through a coaching change, NCAA sanctions and so much that was out of his control, his high school coach, Bruce Rollinson, said, "I truly believe that Matt Barkley saved USC football."
Kiffin said comparing Barkley to Heisman Trophy winners Matt Leinart and Carson Palmer and other Trojans quarterbacks would not accurately reflect his performance or contributions during USC's darkest times.
"I'll remember Matt Barkley as somebody that was so strong through all of this," Kiffin said. "The way he treats people and who he is."
Athletic Director Pat Haden said Barkley "should go down as one of the greatest Trojan athletes of all time."
A year ago, standing before that Christmas tree, Barkley said he was coming back because he wanted to "finish this exceptional and unique journey that I've had here at USC."
He could not have imagined how it would play out.
But Barkley did not sound regretful last week in a short address to teammates, family members and donors at the Trojans' annual awards banquet.
Barkley, steadfast and smiling, described himself as "a Trojan for life" and said being a team captain and representing the senior class ranked among his proudest accomplishments.
"I've learned so much over the last couple years," he told the crowd.
And then, with nary a pause, he added, "Especially the last year . . . how to fight, really fight, and learn what it means to fight on."