American Dalilah Muhammad blew away the field in the third and final semifinal of the women’s 400-meter hurdles on Tuesday, finishing in a semifinal-best 53.89 seconds and establishing herself as the favorite for Thursday’s final.

Muhammad’s U.S. teammate, Ashley Spencer, will join her after posting the fifth-fastest time in the semifinals (54.87 seconds). Spencer clipped the ninth hurdle, but managed to retain her balance and win the second semifinal. Jamaica’s Janieve Russell claimed the other automatic qualifying spot in that heat.

The Czech Republic’s Zuzana Hejnova, who won bronze at the 2012 London Games and is the reigning world champion in the event, tied Denmark’s Sara Petersen for the second-fastest qualifying time of 54.55 seconds. The other qualifiers are Jamaica’s Ristananna Tracey, Britain’s Eilidh Doyle and Jamaica’s Leah Nugent.

Sydney McLaughlin was the only other American in the semifinals. The 17-year-old New Jersey native posted the fifth-fastest time (56.22 seconds) in her semifinal and 17th overall in her Olympic debut.