"This is going to be the hardest sprint spot to make," Richards-Ross said
Sanya Richards-Ross moved closer to a London Olympics 200-400 double while injured sprinter Walter Dix lost a chance for a sprint medal repeat at the US Olympic Track and Field Trials.
Richards-Ross on Friday ran this year's world second-best time of 22.15 to lead eight finalists into a women's 200m showdown that also features 2004 and 2008 Olympic runner-up Allyson Felix, world 100 champion Carmelita Jeter and Jeneba Tarmoh.
"This is going to be the hardest sprint spot to make," Richards-Ross said. "You can run a great race tomorrow and come anywhere from first to sixth. It will take 22 flat, maybe even 21 to win it."
Jamaican-born Richards-Ross, who became a US citizen in 2002, ran the year's best time of 22.09 three weeks ago in a Diamond League triumph in New York and qualified last Sunday for London by winning the trials 400 in 49.28 seconds.
"My body felt good," Richards-Ross said of her semi-final sprint. "I wanted to win so I got a good lane for the final. I'm happy I did that. I was really pleased to see that time. I hope I run faster tomorrow."
Felix and Tarmoh, training partners coached by Bob Kersee, won their heats in identical times of 22.30 six days after finishing in a still-unresolved dead heat for third place, and the final London berth, in the 100.
With a coin flip or run-off due by Sunday unless one declines the spot, the issue will not be settled until after Saturday's 200 final. It has kept them silent to reporters, Felix uttering only "feeling good" about her semi effort.
Jeter and Tianna Madison, trying to set up a London 100-200 double of their own, joined Tarmoh in making no comments Friday.
Dix, third in the 100 and 200 meters at the 2008 Olympics and second in both events at last year's world championships, scratched from his 200 qualifying heat after suffering a left leg injury in the 100m semi-finals.
With his left leg bandaged, Dix was eighth in last Sunday's 100 final. His pullout in the 200, where he ranked fifth in the world this year, means he will miss both sprints at London, but he could be selected for a relay spot.
Also out of the 200 is Justin Gatlin, the 2004 Olympic 100m champion who won the event at the US trials last Sunday. Gatlin scratched from the event after securing his London berth in the 100.
Wallace Spearmon, who was disqualified from a bronze medal spot at the 2008 Olympics for a late-race lane violation, had the fastest qualifying time in the 200 at 20.17 seconds.
"It was a good run," Spearmon said. "We weren't supposed to run that great but it is the first round."
Shawn Crawford, the 2004 Olympic champion and 2008 Olympic runner-up in the 200, was fourth-fastest overall at 20.32.
Angelo Taylor, the 2000 and 2008 Olympic champion, led eight qualifiers for Sunday's 400m hurdles final in 48.77.
"It makes me feel confident," Taylor said. "I'm going in the final with a lot of confidence. I've been here a lot of times. I know what to expect."
Former world champion and 2008 bronze medalist Bershawn Jackson was next in 48.83 and 2008 Olympic runner-up and former world champion Kerron Clement third in 49.04.
"I'm one step away from my dream," Jackson said. "I want to stay focused and bring it home in the finals."
World champion Lashinda Demus led the women's 400m hurdles finalists in 54.41, saying, "They are not going to take me out without a fight. I won't go easily."
Reigning world champion Jason Richardson and Aries Merritt, who has the second-best time in the world this year, were the fastest qualifiers for the 110m hurdles semi-finals, each advancing in 13.13.
David Oliver, the 2008 Olympic bronze medalist, shared the fifth-best hurdles time at 13.32 while Terrence Trammell, the 2000 and 2004 Olympic runner-up, failed to qualify, finishing 24th of 30 in 13.86.
Jill Camarena-Williams, third at last year's world championships, won the women's shot put with a 19.16m effort and Emma Coburn won the women's 3,000 steeplechase in 9:32.78 in the only finals contested Friday.
Janay DeLoach had the best leap in the world this year in the women's long jump at 7.15m while world champion Brittney Reese, whose 7.12 had been the top mark, cleared 6.88 to qualify third among 12 who advanced to Sunday's final.
Beijing Olympic runner-up Hyleas Fountain, coming back after a neck injury, took the first-day lead in the heptathlon with 3,948 points after four of seven events, leading reigning US champion Sharon Day by 151 points.
"My main focus is the Games," Fountain said. "I definitely want to get on the podium. I've been there before so I know what it takes. Once I get to the Games with the confidence I have, I'm sure I will perform well."