But the young gun showed his mettle in front of a capacity crowd estimated at more than 8,000 spectators.
Lillis finished fourth in the men's superfinal in the World Cup stop in Park City, the best finish of any American male aerialist on the World Cup circuit this season. The week of worsts morphed into a day of success with career highs in points and qualifying spots. Lillis had the best night of his career soaring through the air in front of a jam-packed setting.
"Nothing to lose, really," Lillis said. "It's the Olympic year and hometown crowd, and just show what you have. I find when I go bigger and push harder, you know, the result is better than when I try and play it safe."
While Anton Kushnir of Belarus won the World Cup stop, Lillis' performance gave credence to a night in which the U.S. struggled on the hill. Star Emily Cook slipped in her second-final jump, while up-and-comer Ashley Caldwell crashed in qualifiers. Park City resident Dylan Ferguson couldn't stick his second-final jump, which left Lillis, who has been competing in World Cup events for four seasons, as the only hope.
The 19-year-old put down the best jump of his career to win the second-round final and he pumped his first and roared into the crowd as he qualified to go last for the superfinal. But Kushnir, along with fellow Belarusian Alexei Grishin and China's Qi Guangpu, put down solid jumps.
Which left Lillis alone at the top with a chance to podium - or perhaps win - for the first time in his career. But his full-full-full attempt wasn't stuck perfectly. Still, the former moguls skier who transitioned to aerials had a season-best for the Americans.
"I've got as big of tricks as anyone," he said. "On any given day I'm as good as anyone."
U.S. aerials coach Todd Ossian said his youngster is warming up at the right time with two more World Cup stops in the next seven days in the weeks leading up to the Sochi Games in Russia.
So can Lillis be a surprise star in Sochi?
"I think we saw that tonight," Ossian said. "I think his jump that put him into first place going into final round is the same trick that won the Olympics in Vancouver, performed equally as well."
Despite the slip on his final jump, Lillis said he's always sported the mantra of most aerialists of not holding anything back.
"God didn't make me really fit or really tall or muscular I can't run very far but he made me pretty durable," he said.
The Chinese swept the podium in the women's superfinal aerials as Shuang Cheng, Xin Zhang and Mengtao Xu went 1-2-3. Cook finished seventh overall.
1. Anton Kushnir, Belarus (127.15)
2. Guangpu Qi, China (114)
3. Alexei Grishin, Belarus (112.18)
4. Jonathon Lillis, USA (82.21)
1. Shuang Chen, China (91.65)
2. Xin Zhang, China (88.47)
3. Mengtao Xu, China (78.49)
4. Fanyu Kong, China (65.36)
World Cup freestyle skiing
O At Deer Valley Resort, Park City
Saturday • Men's and women's moguls finals, 7 p.m.