Adelaide - Defending Olympic champion Stephanie Rice was fourth fastest into the final of the 400m individual medley at the Australian Olympic selection trials in Adelaide on Thursday.
The 23-year-old, triple gold medallist at the 2008 Beijing Olympics, is under pressure to make July's London Games after surgery last December to repair damaged tendons in her right shoulder.
Rice, who did not speak to reporters after her heat win, needs to finish in the top two in Thursday's night final to compete in the event at London, but her time of 4:45.70 ranked her fourth.
Blair Evans topped the qualifiers in 4:42.54 ahead of Samantha Hamill (4:44.11) and Amy Levings (4:44.65).
Rice's coach Michael Bohl believes it will take a sub-4:35 time to grab a 400m medley berth in the Australian team at the Olympics. She posted a world record 4:29.45 to win the gold medal in Beijing.
"Her shoulder has been good but we don't want to take any unnecessary risks, she just did what she had to to get through to tonight's final," Bohl said.
"She knows there's a fair bit of pressure on her tonight, she's got to perform, she's not going to make the team because her name's Stephanie Rice, she's got to come up with a good swim."
Another defending Olympic champion Libby Trickett swam the fastest time of her comeback to qualify fifth fastest with 59.90 to go through to the semi-finals of the 100m butterfly.
Jessicah Schipper, the bronze medallist behind Trickett in Beijing, was the quickest in morning heats in 58.35 to make it through to Thursday's night semi-finals.
"That was great. I am comfortably through to the semi-finals and I've swum the fastest time I've done since my comeback," Trickett said.
"That's the first time under a minute since my comeback, so to do that in the heat is exciting and hopefully with a little bit more rest and recovery and a bit more freshness I can go faster tonight and on to tomorrow night (final)."
Trickett, 27, faces a big test to finish in the top two against Schipper, Marieke Guehrer (59.82) and 2011 world championship silver medallist Alicia Coutts (59.21) and qualify for the event at the London Olympics.
Brenton Rickard, the 2009 world champion, was second fastest (1:02.09) behind Christian Sprenger (1:00.89) to go through to the semi-finals of the men's 100m breaststroke.