Ayumu Hirano, Kazu Kokubo out of Aspen

Mark Kohlman/ESPN

Citing injuries, Japanese snowboarder Ayumu Hirano pulled out of Snowboard SuperPipe competition on Thursday at X Games Aspen.

Ayumu Hirano, the youngest male athlete scheduled to compete at X Games Aspen this week and a favorite to win Men's Snowboard SuperPipe, pulled out of competition in advance of Thursday's elimination round, citing a foot injury sustained during practice. Hirano's friend and mentor Kazu Kokubo also pulled out of competition Thursday. Alternates Gabe Ferguson and Mason Aguirre will take their spots, rounding out the 16-man contest.

Hirano, now 15, won silver behind Shaun White at X Games Aspen 2013 and is scheduled to represent the Japanese Olympic team in the pipe next month in Sochi, where he's considered a podium threat.

"When both your top riders can't compete, it's not an awesome day," said agent Carl Harris, who represents both Hirano and Kokubo. "Ayumu sprained his ankle a week and a half ago. We were hoping that it would get better and he practiced the last couple days, but it's just not working; any kind of solid impact is just giving him excruciating pain. We made the decision along with the Japanese national team that it's best to get him back home to Japan to rest up for Sochi rather than risking further injury. It was a tough call, especially with the level of expectation around him this week coming into X Games, but it was the right call."

Hirano won the FIS World Cup event at Cardrona in New Zealand in August, following up a win at the 2013 Burton European Open in Laax, Switzerland, and a second-place finish behind White at the 2013 Burton U.S. Open, both in February. He is one of the only riders to approach the pipe with as much amplitude as White and has been hailed as White's potential successor. He has struggled in the 2013-14 season so far, however, with a sixth-place finish at the Dew Tour's iON Mountain Championships and a 13th-place finish at the first of the U.S. Grand Prix events at Copper Mountain in Colorado in December. He skipped the other U.S. Grand Prix events to focus on his Olympic training.

Kokubo, 25, an X Games competitor since 2004, won bronze at X Games Aspen 2010 and last won a major contest at the 2011 Burton U.S. Open. He missed the cut for finals at X Games Aspen 2013, and has mostly focused on backcountry riding and filming over the past two years.

"Kazu's had nagging neck [aches] for the last three years that have really flared up this week, and he made the decision that he didn't want to risk jeopardizing the rest of his season, since he's filming major parts for the new Capita film and an adidas project," Harris said. "He tore his ACL last February and missed an entire season of filming, so he's making filming and editorial a priority this year."

White, who has won gold in the X Games Aspen SuperPipe for the past six consecutive years, pulled out of the competition earlier in the week to focus his efforts before Sochi.

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