Hitting the water just 15 hours after he won the grueling 400-meter individual medley, Ryan Lochte swam the second- fastest time in 200 freestyle heats Sunday morning.
It could be the start of another busy day for the newest American swimming superstar.
"I did not get to bed until 2 a.m. I am really tired," said Lochte. "But it was a prelim swim so I am not too worried."
Missy Franklin was also in the pool for 100-meter backstroke heats after winning her first medal, a bronze, in the women's 400 free relay Saturday night. She had the second-fastest time, too, and 2008 silver medalist Rebecca Soni ran second in heats for the women's 100 breaststroke.
Semifinals for all three races are Sunday night and medals will be given out for the women's 100 butterfly, the men's 100 breast, the women's 400 free and the anticipated men's 400 free relay.
Lochte said "there is some talk" he will be on the men's 400 free relay team later Saturday, when he will also have to swim in semis for the 200 free.
James Feigen, Matthew Grevers, Ricky Berens and Jason Lezak qualified the U.S. with the second-fastest time in the morning behind Australia.
"At the end of the day it is the coach's decision and they are going to put the best four guys they think are right," said Lochte. "I just have to wait and see if they put me in or not."
Michael Phelps, after coming in fourth behind Lochte in their first head-to- head race at the London Olympics, has been expected to take part in the 400 relay final as well.
It's the race that gave Phelps his most thrilling gold medal in Beijing four years ago, when Lezak rallied in the last 25 meters of the anchor leg to overtake the French.
Phelps dropped the 200 free after U.S. trials, trimming his schedule here to seven events after racing in eight the past two Olympics, otherwise he would have had a race Sunday morning.
Grevers had the fastest heat time in the men's 100 backstroke and Allison Schmitt qualified second-fastest for the women's 400 free final, just .02 seconds slower than France's Camille Muffat.
China's Sun Yang beat Lochte by .21 seconds for the fastest 200 heat. Korean Park Tae-hwan was fifth a day after he lost to Sun in the 400 free after being reinstated from an earlier disqualification.
American Dana Vollmer set Olympic and U.S. records Saturday in the 100 fly and will be the favorite in Sunday night's final.
Also, Brendan Hansen will go for his first individual Olympic medal after qualifying in the eighth and final spot for the men's 100 breast. Japan's Kosuke Kitajima won the 100 and 200 breast at each of the last two Olympics and is trying to become the first male swimmer to win an individual event at three straight games.