"Tony's going to win," Larson radioed his Chip Ganassi Racing team.
"Man, these restarts are crazy. You never know," replied crew chief Chris Heroy.
So Larson went for the win.
He weaved low on the start alongside teammate Jamie McMurray, but quickly surged ahead. Then he blew past childhood idol Jeff Gordon and found himself in a side-by-side race with Paul Menard. Using the apron, his wheels inching dangerously close to the infield grass, Larson quickly cleared Menard.
He gained five spots on the first lap, and now had just three cars in front of him. He again drove low. As Kyle Busch passed his older brother and Stewart for the lead, Larson swept past Stewart and tucked in behind Busch.
He looked inside for the lead, but Busch threw a block that stopped Larson's momentum.
No matter. Second was just fine for the rookie.
"Wow," Larson said after following Busch across the finish line at Auto Club Speedway. "Wow! Wow! Good job!"
Larson was echoing the sentiments of thousands of fans who had just been wowed by a dazzling drive through the pack.
If there were any doubts that he belonged at NASCAR's top level, the 21-year-old answered them at Fontana.
He beat Kyle Busch and Kevin Harvick on Saturday for his first win in a Nationwide Series race, then seemed to use everything he'd learned from watching the big names all those years to nearly steal Sunday's victory, too.
Larson, you may recall, is the former sprint car driver that's been raved about by Kasey Kahne, Stewart and Gordon for years. They'd seen what he could do in a car, including one magical night in 2011 at Stewart's Eldora Speedway, where Larson became only the second driver in history to win in all three kinds of USAC cars in a single night.
Although his interest was in IndyCar, he was snapped up before the 2012 season by Chip Ganassi and placed in a NASCAR driver development program. He was 19 and competing in a stock car for the first time in his life.
He was placed in the K&N Pro Series East and won two races and the championship.
Larson was in a Nationwide car the next year. His debut was bumpy—he was the driver who sailed into the catchfence in a last-lap wreck at the season-opener at Daytona, but Larson went on to finish eighth in the final standings. He raced almost weekly against Kyle Busch, mixed it up with Brad Keselowski and Joey Logano, sometimes Harvick and Matt Kenseth.
Come July, Ganassi was ready to promote him to the big leagues. It meant parting ways with longtime driver Juan Pablo Montoya, who had a relationship with Ganassi spanning more than a decade that included an Indianapolis 500 win and a Champ Car title.
Critics cried the kid wasn't ready. After just two years in stock cars?
Those critics didn't include his car owner, his fellow competitors or Target, which finances the No. 42 Chevrolet.
"It's amazing what Nationwide racing will do for you when you're racing against Cup guys," Kyle Busch said. "It's no surprise Larson is good. He gets the experience there of racing against me, Kevin, racing against guys like Matt Kenseth. Once he got here, he was more ready.
"Now that he's a Cup guy and performing well on Sundays, it gives him the confidence and the belief in himself and his team that he can do it Saturday and Sunday both."
Larson is the fresh new face that represents the future of NASCAR. He's the first to reach the big leagues, but there's a whole crop behind him in 18-year-olds Chase Elliott and Dylan Kwasniewski, Ryan Blaney, and Ty Dillon.
It doesn't hurt NASCAR's diversity initiative that he's Japanese-American with a backstory—his maternal grandparents were among the thousands of Japanese Americans sent to a California internment camp during World War II.
What matters now, though, is what he can do in a race car.
He can be quiet and unassuming. He is, after all, the kid who fell for an elaborate family ruse into his teen years that Santa Claus himself was delivering his Christmas presents. Learning the truth upset him, but that's about the only thing that fazes Larson.
He doesn't get rattled, is never awe-struck in the company of all the big stars he watched on TV as a boy, even as he's lining up next to them on the starting grid every Sunday.
Larson did get annoyed, however, in January when he convinced himself he bombed during his first stint of the Rolex 24 at Daytona, his first career sports car race. But he bounced back, just as he did when he crashed at Daytona, or the five times before Sunday that he'd run second to Kyle Busch or Keselowski or Logano in a NASCAR race.
"I was right on Kyle down the backstretch and it went through my mind, 'I might sweep the weekend here,'" Larson said, smiling. "We will take a second. It seems like I run second a lot in stock cars, but I will take a second."