"I think he'll do even better stuff than I have," Koos, the three-time Olympian and former University of Utah skier, said. "It's really cool to race with him. It's kind of like our careers are crossing a little bit."
The 32-year-old Koos grew up in Wenatchee, Wash. Bjornsen was raised about 90 minutes away in Winthrop, Wash.
"I've known him probably since he was 14-years-old," Koos said. "Sometimes he'd do little ski camps, and you [remember when] see a 14-year-old with talent. The ski world's a really small community, especially in Washington. There are only a couple places that skiers come from."
Coming into Sunday's 30km, each racer had earned a trip to the podium. Koos won the 1.3-kilometer sprint and Bjornsen finished first in the 15-kilometer individual start.
After starting in a massive pack, the skiers soon spread out across the course, and neither Koos nor Bjornsen were out in front.
"I have a little bit of luxury in these races, in that I think I'm the fastest guy in the race," Koos said. "You didn't see me up front. I just tried to ski as relaxed as possible, and when somebody makes a move, I'm going to follow them but I don't have to make the move."
Bjornsen followed suit.
"Any chances I got when I was out there and I could jump behind [Koos], I did," he said. "I feel pretty comfortbale and we ski pretty similar."
With about 10 kilometers to go, pack leader Tad Elliot made his move.
That's when Koos, the seven-time U.S. champion sprinter, sprang.
"I still felt like I had a kick at the end," Bjornsen said. "I couldn't quite match Torin's kick."
30km Classic Mass Start
1 • Torin Koos, Bridger Ski Foudnation
2 • Erik Bjornsen, APU Nordic
3 • David Norris, Montana State University
Women's 20k Classic Mass Start
1. Sadie Bjornsen, APU Nordic
2. Kate Fitzgerald, APU Nordic
3. Sophie Caldwell, Stratton