EUGENE, Oregon (Reuters) - Allyson Felix's dream of completing a rare double at the Rio Games is still alive but a tearful Olympic 400 meters champion Sanya Richards-Ross brought the curtain down on her career at the U.S. Olympic trials on Friday.

Felix, who is bidding to become only the third woman to win a 200-400 double at the same Olympic Games, eased through the opening round of the 400 just minutes after Richards-Ross pulled up injured in an earlier race.

"My hamstring grabbed me," the 31-year-old Richards-Ross, who announced earlier she would retire this year, said after stopping 250 meters into the race.

"I've had an amazing career," the three-time Olympian said. "To have my last race be here, at Hayward Field, in front of these fans, it's incredible."

She blew kisses to the crowd, which rose to show its appreciation for her 16-year career.

“No Rio. No Rio," she said. "That’s the toughest part. You really want to go to the Olympics. No matter how banged up you are you still think it’s possible."

Felix, still running in pain from an April ankle sprain, left for medical treatment without speaking to the media.

She finished a comfortable second in her preliminary race. Her time, 51.96 seconds, was well off her personal best but good enough to advance to Saturday's semi-finals.

Olympic silver medalist Galen Rupp won his eighth consecutive 10,000 national title and fellow Oregon native Ryan Crouser claimed the shot put, the only finals on the opening session of the 10-day trials that will determine the U.S. team for Rio.

Rupp, already the winner of the American marathon trials, pushed to the front for keeps in the final 400 to win in 27:55.04. He is thinking of running in both events in Rio with an eight-day gap between the 10,000 and the marathon.

Kenyan-born Shadrack Kipchirchir (28:01.52) and Leonard Korir (28:16.97) join him on the U.S. team.

Crouser upset shot put world champion Joe Kovacs with the second-best throw in the world this year of 22.11 meters.

Kovacs (21.95m) still made the Rio team as did third-placed Darrell Hill (21.63m).

The biggest qualifying upset came in the men's 800 where the year's fastest American, teenager Donavan Brazier, was eliminated in the first round.

Brazier, who broke Jim Ryun's collegiate record last month with a sizzling run of 1:43.55, finished outside the qualifying spots with a time of 1:48.13.

Olympic long jump gold medalist Brittney Reese and world indoor champions Boris Berian and Vasthi Cunningham moved comfortably through qualifying.

Reese leaped 7.01m, Berian ran the 800 in 1:46.03 and Cunningham was one of four high jumpers to clear 1.84m.

(Editing by Peter Rutherford)