EUGENE — Two Americans, including former Oregon Ducks standout Alaysha Johnson, stumbled during the women’s 100-meter hurdle heats while two others advanced to the semifinals.

Nia Ali, the 2019 world champion and silver medalist at the Rio Olympics, was on her way to winning the first heat Saturday morning at the World Athletics Championships at Hayward Field, but her left trail foot clipped the ninth hurdle and she fell into the 10th before hitting the track.

Later, Johnson appeared to move to her set position late and left the blocks awkwardly, with the slowest reaction time in the fourth heat, before hitting the first two hurdles and walking the rest of the way down the track after that.

Johnson had been considered a medal contender. She recorded the second-fastest time in the world this year, 12.35 seconds, in finishing as runner-up in the event at the USA Track & Field Outdoor Championships last month at Hayward Field.

Neither Ali nor Johnson stopped for interviews afterward.

World record-holder Kendra Harrison won the sixth heat in 12.60 seconds, fifth-best among the 24 women to advance to Sunday’s semifinals, and NCAA champion Alia Armstrong won the fifth heat in 12.48, second-best on the day, to give the United States two women in the semifinals.

“I think in the semis I have to be a little bit more aggressive,” said Harrison, who won silver at the Tokyo Olympics last summer. “I think I played it safe today and my coach won’t be happy, but it’s fine. My start — the blocks, we didn’t use those blocks out there. I got to figure out the settings, but other than that I’m pleased to make it through.”

“I wanted USA to get 1-2-3. So we got to represent Team USA the best that we can and try to make it through these rounds. But it’s a shame to hear that (Ali and Johnson) didn’t make it through.”

Armstrong, 21, has turned in her two best times in the event at Hayward Field and could contend for at least a spot in the final in her first world championships.

“I feel as though I got out and I just increased my frequency and I got quicker and quicker down the track,” Armstrong said. “The more I got down the track, the more confident I got. I feel like that was a big part of my success in the race. To be honest, I wanted to come out here and do the best I could and win. The fact that my teammates won’t be next to me, I just want to do it for them. I pray for them that their mental is OK, but I’m going to go out there and I’m going to do the best I can for them.”

Tokyo Olympics gold medalist Jasmine Camacho-Quinn of Puerto Rico cruised to a win in the second heat in 12.52 and African champion Tobi Amusan of Nigeria dominated the fourth heat in 12.40.

“I took it pretty easy,” Camacho-Quinn said. “I didn’t want to go too hard; I just wanted to make it through safely. I mean it’s the first round so, just get prepared for tomorrow for semis.”

Both Camacho-Quinn and Jamaica’s Megan Tapper, the bronze medalist in Tokyo, were disappointed for Ali and Johnson.

Tapper finished in 12.73 despite struggling over multiple hurdles in what she acknowledged was a “super rusty” race.

“It’s understandable, my performance, in my opinion,” Tapper said. “But I’m coming back for more in the semis with fire, with vengeance.”

The semifinals are scheduled for Sunday evening.

— The Oregonian