Immersed in their pre-competition cocoons, the three leaders in the men's short program Friday had no idea what the fourth-ranked skater had done. Once they heard about Nathan Chen's history-making performance, they were mightily impressed — and delighted at what Chen's two-quad feat means for American skaters.

Chen, 16, became the first skater to land two quadruple jumps in a short program at the U.S. championships. He and leader Max Aaron, who hit a quad salchow, were the only two men in the field of 19 to successfully complete quads on Friday.

A day before, U.S. Figure Skating President Samuel Auxier said American skaters must master those difficult jumps if they hope to challenge for medals at the Olympics and world championships. Chen is the only competitor who plans three quads in Sunday's free skate, and his rivals admire his willingness to aim high.

"For him to be so young and able to do that is a huge step in our sport," said Aaron, whose free skate includes two quads. "I love seeing him push the boundaries.

"[American men] need to be better when we step out on world ice and go against guys like [Canada's] Patrick Chan and [Japan's Yuzuru] Hanyu, who's doing three quads. We need to be able to be competitive. If it takes a 17-year-old to push the limit in the U.S., it will wake me up."

Only eight of the 19 men skating Sunday include quads in their long programs, and only four plan to try two or more. Aaron's training partner, 15-year-old Vincent Zhou, has two; Adam Rippon, in third place after the short program, has one.

Chen has been landing quads since age 14 and is doing the quad salchow and quad toeloop. Rippon trains alongside Chen, and he has seen him try as many as four in a single program.

"Nathan doing two quads in the short program is really important for the development of U.S. men's skating," he said. "It's what's happening in the world right now. I think he's an incredible skater, and I think he's the future."

Brown to Worlds?

2015 U.S. champion Jason Brown was unable to defend his title because of a back injury, but he has not given up hope of making the world championships team. Brown has filed a petition with U.S. Figure Skating asking to be considered for the team, which will be named Sunday after the nationals conclude.

Brown withdrew from the U.S. championships on Jan. 7 because of a back strain, which also forced him to drop out of NHK Trophy in November. Coach Kori Ade told that Brown will return to training next week and has enough time to prepare for the world championships, which will be March 28-April 3 in Boston.

Last year, Brown finished fourth in his world championships debut. The U.S. will send three men to worlds, including the 2016 national champion and two skaters chosen by U.S. Figure Skating's international committee.

Worlds and more

The U.S. roster for the world championships will include 16 skaters. Based on their performances at the 2015 worlds, the Americans earned three spots in the field for women, three for men, three for ice dance and two for pairs.

The international committee also will select two other teams Sunday, naming the rosters for the 2016 world junior championships and Four Continents championships.