RUBY — Rick Casillo sat on the back of his camouflage sled Friday, peeling off soggy socks and contemplating ending his race here, at the Yukon River village roughly 500 miles into the Iditarod Trail Sled Dog Race. He had sent his main lead dog, Nick, home.

"This was the greatest mushing I've ever experienced," said Casillo, who has finished all six of his Iditarod races and in 2006 was named most improved musher. "It was awesome, and it changed in an instant. I went from a top-20 position to probably going home, which sucks."

Nick was bitten on the wrist on the trail between Cripple and here. The 5-year-old dog had stopped to smell urine.

"There's a lot of females in heat out on the trail, so they're peeing everywhere and he was immediately locked up to the smell," Casillo said. The dogs kept running and an animal farther back in line bit Nick's wrist right at the joint. Casillo said he had no idea and Nick, a 60-pound dog, continued running for about 10 miles. Then he started to slow.

The next stop for Nick was in the sled bag for a ride in to Ruby, his 10 teammates pulling. He then took a flight back home and Casillo sat, left to answer a big question: What's next? Did he want to end his race? Could he make it past the coast? He said he didn't think he had any other dogs interested in leading the pack. But nothing's certain.

By early Friday evening, Casillo had taken off his dogs' harnesses as they lay in straw. He still sat in 27th place and planned to go to sleep himself. Once he woke up, he would decide whether, this year, he and his 10 remaining dogs would ever reach Nome.

Casillo is the musher who four years ago started Battle Dawgs for combat veterans, aiming to "change and save lives," he said earlier this week. The nonprofit connects veterans with the outdoors and promotes teamwork in an effort to shrink suicide rates, Casillo said. He takes the veterans on glacier tours, ice fishing trips and asks them to help out with the Iditarod. This year, he flew three veterans to the Rainy Pass checkpoint.

When Casillo pulled into the Rainy Pass checkpoint earlier in the race, the veterans held up a camouflage flag that said "Battle Dawgs" in white print underneath a large paw-print. Casillo has a camouflage sled bag with a patch that had the number 22 crossed out. Each day, he said, 22 veterans commit suicide.

While Casillo isn't a combat veteran himself, his wife is a lieutenant colonel in the Alaska Air National Guard. He's always had a passion for helping those who enlisted.

"What sucks the most is I let my warriors down, and that's what hurts," Casillo said. "I'm the one they're watching."