He pulled off the greatest statistical upset in college football history over four years ago, became a significant contributor to the turnaround of the Stanford program and has already spent a full season as a volunteer assistant for the squad. But believe it or not, Tavita Pritchard still has a lot to learn about football.

And he’ll admit it as quickly as anybody.

That’s because, despite having thrown for 2,865 yards and 15 touchdowns in 31 career appearances wearing Cardinal, Pritchard has now set his sights on defense.

“Right now I’m really just trying to be a sponge and trying to be a student of the game,” Pritchard said. “And it worked out staff-wise for me to be able to be a defensive staff assistant, and I jumped at the opportunity to be on this staff and get to work with [Co-Defensive Coordinators] Derek Mason and Jason Tarver. It’s a tremendous opportunity for me to learn football and defensive philosophy from them.”

“I’m just trying to take as much in as I can, learn as much as I can, for when I do coach down the road–be it on offense or defense–I’ll be the best prepared that I can be,” he added.

Early returns indicate that Pritchard is headed in the right direction.

“Well, we got lucky enough that they were going to let us have Tavita, number one, because he’s excellent: He has work ethic, he has intelligence and he’s a Stanford guy so he’s got to be pretty smart,” Tarver said. “You tell him something, he gets it done.”

And as the Cardinal heads back into the L.A. Coliseum this weekend riding a two-game road winning streak against USC, Stanford fans will be remembering Oct. 6, 2007, when Pritchard got something quite memorable done.

Coming in as a 41-point underdog against the No. 1 team in the country and with then-backup Pritchard making his first career start in one of the largest stadiums in college football, nobody was surprised when Stanford failed to score an offensive touchdown in the first three quarters. But the Cardinal hung around behind a stifling defensive performance, and a 37-yard pass to redshirt senior Mark Bradford to the Trojan 1-yard line helped put Stanford within just two points of USC early in the fourth quarter.

After the Trojans added a touchdown and Stanford made a field goal to make the score 23-17, an interception set the Cardinal up at the USC 45 with three minutes to play in the half. Then the madness really began. A pass-interference penalty moved the ball up 15 yards. A botched halfback pass was salvaged by freshman running back Jeremy Stewart, who turned the play into a 4-yard gain. (“I still give him a hard time for not throwing me the ball,” Pritchard said of the current redshirt-senior.) A call lost in translation between Pritchard and head coach Jim Harbaugh on fourth-and-20 turned into a tight-window pass for the first down–on a play chosen by Pritchard, no less.

And a perfect floater from the then-sophomore found a leaping Bradford in the end zone for the game-winning touchdown, sending the college football world into convulsions, ending the Trojans’ title hopes and reviving the spirits of the downtrodden Stanford faithful.

All that, and Pritchard still doesn’t own a “Biggest Upset Ever” t-shirt.

“I think somebody told me they were going to give me one, but they never followed through, so I’ve yet to see that come to fruition,” he joked.

That doesn’t mean Pritchard is oblivious to the significance of “the USC game,” however.

“Absolutely, I’m very proud of what my class and the classes above and below me did,” Pritchard said. “I know that game really serves as a marker, but it was just a manifestation of a bigger change in this program…Guys just saying, ‘Hey, we can be good at football. We can be great at football here, if we just start doing things right.’”

“So I’d say a lot of people look at that game as a marker of this program righting the ship, but that’s all it really is: a marker,” he added. “Because the work is done out here on the practice field, and in the building.”

And despite the historic win over USC, Pritchard still had his work cut out for him as a Stanford quarterback. After sharing time with T.C. Ostrander in 2007, Pritchard took over the starting job the following season and led the Cardinal within a win of its first bowl game since 2001. Even when his playing days seemed to be shortened as a senior by the emergence of one Andrew Luck, Pritchard was called upon again on a big stage when Luck broke his finger before the Sun Bowl–much like he stepped in against USC after Ostrander had suffered a seizure less than a week beforehand.

When the Cardinal fell short in a tight 31-27 game, it looked as if Pritchard’s time on the Farm would end on a losing note. But he had something else in mind.

“I told [then-head coach Jim] Harbaugh before the next season that I wanted to get into coaching, that I thought I owed it to myself to at least try it out,” Pritchard remembers. “And coach Harbaugh said, ‘Great. Come on. I don’t have any staff positions open, but you can come volunteer.’ And I did everything from filling up coach Harbaugh’s refrigerator with Diet Pepsi to breaking down film.”

Harbaugh moved on to coach the San Francisco 49ers this season, but Pritchard still has “fond memories” of the man he cites as instrumental to both his own development and the Stanford program’s.

And as the David Shaw era began on the Farm, Pritchard reached a turning point of his own. Taking up his first-ever paid coaching position on the defensive side of the ball, he spent the offseason learning from Tarver, Mason and–perhaps just as importantly–the players.

“Now I’m starting to see the game from the other side, how they actually teach it and all the adjustments and techniques they teach,” Pritchard said. “So it’s a little bit of give-and-take. I’m able to relay some of my knowledge as a quarterback to the defensive backs, and at the same time, I’m able to learn stuff I wasn’t really able to learn on the offensive side.”

A long-time quarterback who hasn’t played defense since high school–coached by his father David, the offensive coordinator at Clover Park High in Washington, he was inserted only to defend against Hail Mary passes–Pritchard was a natural fit to work with the Cardinal secondary.

“What’s great is that you get to know the ball through different eyes,” Tarver said. “Right now, he’s throwing deep balls to the DBs, but he knows where the quarterback’s going to put it, so he’s got knowledge to teach them as to where the quarterback’s going to throw the ball. So you see it from a different set, because everybody comes into football and sees it the way that they were raised in it…it broadens your perspective as a coach.”

Who better to oversee Pritchard’s transition than Tarver? He was a defensive back by training who served in various defensive assistant roles at the college level from 1996-2000, worked on the 49ers’ offensive staff for the four subsequent seasons and then went back to the defensive side of the ball, coaching San Francisco’s outside linebackers between 2005 and 2010 before coming to Stanford this season.

And working with a Stanford backfield that has its fair share of players that started on offense, Pritchard has run into some familiar faces. Senior strong safety Delano Howell took handoffs from Pritchard in 2008 as a freshman running back and caught nine passes for 94 yards that year.

“It didn’t take him too long to master the whole defense,” Howell said. “He puts time into it, he’s very passionate about everything he does–just like when he was a quarterback…He’s put himself in a position where we can respect him, we can look up to him; not only is he a coach, but he’s a friend as well.”

Those sentiments are echoed emphatically by Tarver.

“Tavita’s doing great,” he said. “He’s the best, he’s already a great coach and he’s going to be whatever he wants to be. He’s that good.”

But even though Pritchard seems to have a knack for coaching, he’s not quite sure what he wants to do next. He just hasn’t had time to think about it.

“Our goal is to play in the Rose Bowl, and I can’t see beyond that,” Pritchard said. “The season, man, it is a grind and it’s a lot of fun hours up in the office, but I can’t see beyond that. I’m coaching for now, I’m going 100 miles an hour and doing the best I can, and we’ll see when I come up for air in the winter and in the spring. We’ll see what happens.”

So this week, Pritchard has his sights set back on USC (6-1, 3-1 Pac-12), which is unranked due to NCAA sanctions but clearly one of the top teams in the Pac-12. And when No. 6 Stanford (7-0, 4-0) returns to the Coliseum for just the second time since the Biggest Upset Ever, it’s bound to be favored over the once-powerhouse Trojans for the second consecutive year.

“We’ll all look back on that game with fond memories,” Pritchard said of that fateful night in 2007. “And I’m great with that. I love being a part of the Stanford community and being a part of this football program, because it’s what we always wanted, what you see now: us competing on a national stage. It’s what we all had envisioned and we knew it wasn’t going to happen overnight. So if that’s a marker for the change in the times here, great.”

“And I’m proud to be a part of it, for sure,” he added. “However a small part that I played, I’m very proud of that.”