Galen Rupp hits the tape to win the 10,000 meters event at the U.S. track and field championships in Eugene, Ore. Rupp, who wore a mask for most of the race to protect him from a high pollen count, won with a time of 28 minutes 38.17 seconds. (Don Ryan/Associated Press)

He looked like a bank robber. Or a hockey goalie, or Darth Vader. Galen Rupp started the men’s 10,000-meter final on Thursday night at the U.S. track and field championships wearing a mask designed to filter pollen out of the air. But he threw it onto the track late in the race so he could make the sprint he needed to claim his third national title at the distance.

Once Rupp ditched the mask, which covered his face from the nose down, he slipped to the front of the large pack of runners that had turned a 25-lap marathon into an 800-meter sprint to the finish.

And Rupp blew away the field.

He crossed the finish line in 28 minutes 38.17 seconds, outkicking Matt Tegenkamp (28:39.97) and Scott Bauhs (28.40.51). The race offered all the drama lacking in the women’s final just before, when 2008 Olympic bronze medal winner Shalane Flanagan took and early lead and dominated, winning in 30:59.97. Kara Goucher got second in 31:16.65 and Jen Rhines claimed third in 31:30.37.

The mask “helped,” Rupp said. “I know it looks silly. I get embarrassed wearing it to be honest with you. . . . But if it’s going to help me out . . . that’s the most important thing.”

Rupp, who said he is extremely sensitive to pollen, wore the mask during a half-marathon in New York last fall, but had never used it during a major track event. With the pollen count registering high here today, he followed the advice of his coach, Alberto Salazar, who didn’t want him to risk an allergy attack. Rupp had pulled out of a race at the Prefontaine Classic here just three weeks ago because of the poor conditions. Thursday, he had to be ready to race.

Though the mask helps early, Rupp said, it becomes increasingly uncomfortable when it heats up and rubs against his nose, cheeks and chin. He said Salazar told him to throw it off when he couldn’t take it any longer.

“It was lucky we went out a little slow,” Rupp said. “I kept it on a long time.”

Rupp went to the front with three laps remaining and turned on the heat, finishing with last laps of 65.3, 58.2 and 54.4 seconds. Tegenkamp stayed on his back but couldn’t close the gap, then watched Rupp run away with the race over the final 200.

“You sit there and just wait; you think you got the best kick,” Tegenkamp said. “We turned into 1,500 meter runners. All the credit to Galen. He ran tough. . . . I just didn’t close it. Pretty simple. He just ran away from me.”

Flanagan did the same.

Only much earlier. The victory came seven months after her second-place finish in her debut marathon in New York. Flanagan said the heavy base of marathon training seemed to help her transition back to the track this summer.

“I felt like I hit a nice rhythm,” Flanagan said. “I just felt really natural, not pressing. . . . I just made sure to seal the deal in the last lap.”

Goucher, who gave birth to her first child nine months ago, said she was thrilled with the finish — and with qualifying for the summer’s world championships in Daegu, South Korea.  After dabbling in marathon running, Goucher said, she was ready to get back to the track, where she won a bronze medal at the 2007 world championships. In her most recent race, this year’s Boston Marathon, she finished fifth.

“I have missed the track a lot,” she said. “There was this expectation that I would just nail this marathon thing. I’ve done four marathons now, and I feel like I really struggled in all of them.”