Barkley faced off against another Clarkson client in Ohio State's Terrelle Pryor in the Trojans' 18-15 win over the Buckeyes on Sept. 12.
The following weekend the quarterback guru was in attendance when two of his high school clients met in a nationally televised game in Sammamish, Wash., a Seattle suburb.
Oaks Christian (Calif.) senior Nick Montana squared off against Skyline (Wash.) senior Jake Heaps in Oak Christian's 28-25 victory. Montana is the son of NFL Hall of Famer Joe Montana.
"I was actually there for two games," Clarkson said last month while in the area working out Red Lion Christian Academy seventh-grader David Sills. "I had [Washington quarterback] Jake Locker. Jake Locker and Matt Barkley were both supposed to start in the USC-Washington game when I made the trip. But Barkley got hurt."
So he settled to witness Montana produce a come-from-behind victory reminiscent of his father's NFL exploits. In addition to Montana, Clarkson has worked with Trevor Gretzy, son of Wayne Gretzy, and Corde Broadus, son of Calvin Broadus, Jr. (a.k.a. Snoop Dogg).
His list of clients includes NFL players Ben Roethlisberger, Matt Cassel and Matt Leinart.
The former standout San Jose State quarterback is sought out because his endorsement and tutelage has become the gold standard for young signal callers.
If the 48-year-old likes what he sees and makes you his client, it's time to start pondering which college you want to play for. But getting picked is tough and expensive.
Clarkson is very selective. His list of clients is the football equivalent of getting into Massachusetts Institute of Technology (MIT). And be prepared to spend a lot of money.
The cheapest deal is around $625 a month. That includes 48 sessions a year but no one-on-one instruction.
"On the private [instruction] side, I work with 24 kids," said Clarkson, a Pasadena, Calif., resident who has clients all over the country and in Germany, England and Japan. "That's all I can work with, because of the time, travel and getting on airplanes.
"You are not going to get into that 24 for less than $8,000 a month."
And that's assuming you pass a private two-day evaluation that costs $3,000 plus traveling expenses.
"I've been training with [Clarkson] since I think the summer after I turned 10. So about three years," said Sills, 13. "Usually during the season, he will come out here two to four times. Usually, we will go out to him in the off-season like once every month and a half."
More knowledgable than your typical seventh-grade quarterback, Sills spends his free-time breaking down film of Tom Brady and Peyton Manning. He's also mastered pre-snap reads.
"He is extremely special," Clarkson said. "I first saw it with Jimmy Clausen. If there was a LeBron James in football, Jimmy Clausen would be the one. Then Matt Barkley was sort of second.
"This one [Sills], he is so unique. I thought he was the Tiger Woods of his position."
Sills credits his success and poise to Clarkson, who said he never set out to become a renowned quarterback coach.
Despite holding several school passing records in college, he went undrafted in the 1983 NFL draft. He played a season for the Denver Broncos and two seasons for the Canadian Football League's Saskatchewan Roughriders.
"I came out at a time when the black quarterback wasn't really getting an opportunity," Clarkson said of not getting drafted.
"But in my mind, it wasn't anything I could do," he added. "And I was OK with that."
Done with football in 1986, he was a regional manager for Black Angus restaurant when began working with high school quarterbacks on the side. His first student, Perry Klein, was a volleyball player who had never played football before.
Under Clarkson's guidance, Klein completed 46 of 49 passes for 567 yards and eight touchdowns in his first game. Through his connections, Clarkson helped Klein, who later set California high school records and played with the Atlanta Falcons, get national media attention.
"So I started getting calls from all over the country from parents, who basically wanted me to do this for their kid," he said.
And he's been training blue chippers ever since.
"The funny thing was here is a guy who was an NFL reject, who they said for whatever reason ran a Canadian-style offense" in college, he said. "Now, they come to me to find their next great one. So that's the irony of the whole thing."
Contact staff writer Keith Pompey at 610-313-8029 or firstname.lastname@example.org.