EUGENE — There are no sure things in the wacky world of pole vault. Even so, it’s not bad being Brad Walker right now.

The defending world champion broke an eight-year-old American record Sunday at the Prefontaine Classic, clearing 19 feet, 93⁄4 inches on the same field where he’ll try to make his first U.S. Olympic team in only three weeks.

“The track’s good, we’ll say that,” Walker said. “Eugene, when the weather’s nice, is probably one of the best places to jump. The American record’s here for me now. I know that it’s a great place to jump. I know I’m confident that I can jump high here, so it just adds to my confidence for the trials.”

Walker broke the record held by Jeff Hartwig at 19-91⁄4. Then, Walker took two shots — after skipping the first attempt to catch his breath — at Sergei Bubka’s world record of 20-13⁄4, but didn’t come close.

Still, it was hard to label this day anything but a triumph for the 26-year-old, two-time U.S. outdoor champion — and it was made even better because one of the guys he beat was Hartwig himself.

“I always thought if I did it, I’d want to do it at a meet that Jeff was at,” Walker said. “We’re great friends. We’ve talked a lot over the years. He’s given me pointers. He hugged me and told me ‘Good job.”’

Walker shared the spotlight at America’s biggest track meet with Maria Mutola, the middle-distance star from Mozambique, who won the 800 meters for the 16th straight year in this, her final appearance at Prefontaine.

Mutola kissed the track after the race.

“All the emotion, the stress is behind me now that I was able to finish good,” she said.

China’s biggest track star, Liu Xiang, lined up for the 110 hurdles, but flinched early and was disqualified for a false start, turning his trip to America into a nonevent. He scratched from last weekend’s meet in New York with a sore hamstring and was apparently well enough to run Sunday, but didn’t get his chance.

Asked what happened on the start, he said, “nothing happened.”

“I didn’t even realize I had the false start,” Liu said.

Other winners included former world champion Torri Edwards, who ran the 100 in 10.94.

After missing the Athens Olympics because of a doping ban she received even though authorities ruled she wasn’t intentionally trying to cheat, Edwards appears to be rounding into form for a bid to Beijing while others are struggling. Allyson Felix, the world 200 champion, finished fourth, while world 100 silver medalist Lauryn Williams finished sixth, failing to make the top three for the second straight week.

“There’s a lot of talent in the 100 meters, a lot of women who have dropped under 11,” Edwards said. “The trials is going to be exciting.”

Sanya Richards won the women’s 400 in 50.10 seconds.

Bernard Lagat, a naturalized American citizen since 2004, had a chance to set the American record in the rarely run two miles, but finished in 8:12.45, more than 5 seconds off the record pace.

Ethiopia’s Kenenisa Bekele failed to improve his world record in the 10,000, but still finished in 26:25.97, the fourth-fastest ever.

And another Ethiopian, Meseret Defar, fell short of her bid to regain the world record taken from her countrywoman, Tirunesh Dibaba, two days ago in Oslo. Defar won in 14:38.73, nearly 38 seconds off the new world mark of 14:11.15 set by Dibaba.

Despite those shortfalls, eight meet records were set on a gorgeous, sunsplashed day at Hayward Field on the University of Oregon campus.

American athletes will come back here for two pressure-packed weeks beginning June 27, trying to secure their spots in Beijing. Some of them, like Tyson Gay, Jeremy Wariner and Lagat, can pretty much book their tickets right now.

Others, like, say, anyone in the pole vault, will simply have to wait until showtime.

It is, indeed, a crap shoot, maybe illustrated best by the fact that Hartwig himself, holder of the American record for almost a decade, didn’t qualify for either of the last two Olympics. Now, at age 40, he’s considered a long shot.

“You accept what your event is, that anything could happen at any time,” Walker said. “I’ve broken my thumb, I’ve seen people end up with stitches. You accept it for what it is, but you just don’t focus on what could go wrong, because if you do, you’re focusing on the wrong thing.”

Despite all that, Walker is as good a bet as anyone to make the American team, and if he gets there, anything’s possible. His mark of 19-93⁄4 was the highest vault by anyone, anywhere, in seven years.

“I’m confident, you know, but I’m never going to overlook the pressure and the competition at trials,” he said. “I still need to focus and still need to make sure that everything’s in working order by the time I get there.”