MOSCOW â A young woman who has handled the day-in-day-out pandemonium of having six younger brothers is not likely to panic at the prospect of facing seven other hurdlers.  âTheyâre always energetic and itâs sometimes annoying, but I love them to death,â Brianna Rollins said of her siblings.  Rollins is, at least until Sunday, just 21 years old, which should make it easy to remember that she is also the fastest womenâs 100-meter hurdler in 21 years.  Her winning time of 12.26 seconds at the United States championships in June was the sort of performance that makes track geeks do cartwheels into the Des Moines night.  It was a North American record, better than Gail Deversâs 13-year-old mark of 12.33. It was also only five-hundredths of a second short of the long-elusive world record, set by Yordanka Donkova of Bulgaria in 1988.  âHurdlers usually peak at around 27 years old,â said Joanna Hayes, the 2004 Olympic gold medalist in the 100 hurdles from the United States. âWhat Brianna is doing just isnât done. Itâs fair to call her a hurdle prodigy.â  Now for the tricky part: she is a hurdle prodigy with very experienced, accomplished competition.  The potential opposition for Saturdayâs final at the world championships includes Sally Pearson, the reigning world and Olympic champion from Australia, and Dawn Harper, the American who won the 2008 Olympic title and finished second to Pearson last year at the London Games.  Rollins has never raced Pearson, who ran 12.28 when she won the world title in 2011 and dominated the event until this season, when a series of hamstring injuries have slowed her progress. But Pearson has pushed to be healthy for the world championships and looked sharp in her opening round Friday.  Pearson and Rollins were initially scheduled to race in Monaco last month, but Rollins did not take part in the meet, prompting suggestions that she was dodging Pearson until Moscow.  âItâs not true,â Rollins said. âMy coach and I had a plan on what I was going to do when I was starting my professional career. This is my first time running in Europe, so we wanted to come out here and just see and get the feel of it and see how it is to run overseas and just get my body used to it, because Iâve never done it before. So it was no dodging anybody. It was just coming up with a game plan for myself and not thinking about anybody else.â  Any duel with Pearson here depends on both of them surviving the semifinal round Saturday. Rollins, Pearson and Harper are all remarkable technicians.  âWhen I tell young athletes to go on YouTube and watch hurdlers, those are three I tell them to watch,â Hayes said.  But only Rollins has gone below the 12.50 mark this season, which in her case was well below.  âOf the three, Briannaâs gone the fastest already, but Dawn and Sally both have global titles,â Hayes said. âBrianna has nothing yet except for U.S. titles and the American record. Weâre kind of waiting to see how she handles international pressure. Judging from the first round, it looks like she handles it just fine.â  Rollins had the fastest time in qualifying Friday, but this is still new territory for her. This is her first summer as a professional after winning three N.C.A.A. titles in the 100 hurdles at Clemson. This is her first major international championship after failing to make the Olympic team last year, a disappointment she has used for fuel.  âThat was very motivating,â Rollins said in an interview at the American teamâs hotel in Moscow this week. âEspecially being that I was really young. I was like, I can compete against these girls. I just need to take these things serious.â  Rollins said she was lacking something in practice despite her consistent collegiate success.  âAsk my coach, I hated practice; I used to quit,â she said. âIf I started hurting, I used to just lay on the ground for a good long minute, no, three minutes, and not finish a workout.â  Rollins, who trains with the American hurdler Queen Harrison under the former Clemson coach Lawrence Johnson, also attributes her big move this season to being healthier and able to lift weights more intensely instead of protecting an ailing hamstring or a fragile back.  Although she is a debutante at this level, she is well aware that the lower her time goes, the more questions will be posed.  âItâs very unfortunate, but this is what happens in our track and field environment,â she said. âIt comes with it, I guess. Just try to block out all the negative energy and try to stay focused and stay positive.â  For the record, and it matters to Rollins enough to put it in her Twitter biography, her first name is pronounced BRY-anna, with the first syllable rhyming with try.  Asked to explain how she became the person she is today, Rollins thought for a while.  âWhat made me me?â she said. âI do feel like I came from humbling grounds, so I think thatâs why I am so calm. I came from a family with six younger brothers. We werenât that fortunate as far as moneywise, so I just think coming from a family like that, it humbles you. It keeps you motivated and makes you want to do great things so that you donât have to, later in your life, live like that again.â  Hayes and others believe great things are definitely in reach.  âThe world record is possible,â Hayes said.  That is a rare thing to be able to say in womenâs track, where the world records in the sprint events â from 100 to 400 â all date to the 1980s, as does Donkovaâs record.  Rollins said she has watched that race on YouTube.  âJust to see what a 12.21 looks like,â she said.  So, how did it look?  âPretty fast,â Rollins said with a grin. âPretty fast.â  This article has been revised to reflect the following correction:  An earlier version of this article misstated the day of the preliminary heats. They were Friday, not Thursday.
Brianna Rollins, 21, the U.S. record holder in the 100-meter hurdles, may face two former Olympic champions on Saturday when she is tested internationally in the world championships.