Irvine - Michael Phelps, gunning for a spot on his first national team since the 2012 London Olympics, was third-fastest in 100m freestyle qualifying Wednesday at the US Swimming Championships.
The 29-year-old superstar, whose 22 Olympic medals include 18 gold, said he'll have to do more in Wednesday night's final, when he'll be up against 100m free Olympic gold medalist Nathan Adrian as well as sprinter Anthony Ervin -- the top two qualifiers.
Adrian topped the times with a swim of 48.24sec. Ervin was second-fastest, winning his heat in 48.71 while Phelps, second to Adrian in their heat, clocked 48.77.
The championships are the selection meet for the Pan Pacific championships August 21-25 in Australia's Gold Coast.
The PanPacs, featuring the United States, Canada, Australia, New Zealand, Japan and Brazil, are the biggest international meet for US swimmers this year and along with this week's competition will help determine the team for the 2015 World Championships in Russia.
Adrian didn't match his season best of 48.08 from the Mare Nostrom meeting in Barcelona, but his 50m split of 22.63 showed up Phelps.
Phelps made the turn at 23.98.
"Pretty terrible first 50," said Phelps, adding he knew he was a body length behind Adrian at the halfway mark.
"The stroke was pretty terrible the first 50 -- I think it's a matter of getting into the stroke better in warm-up."
The 100m free was never one of Phelps's individual Olympic events but he was a strong enough performer in the race to be a staple of the US 4x100m free relay team.
"These guys, Nathan and Anthony are going to be out so fast," Phelps said. "I'll be honest, I probably don't have that speed. It's a matter of being able to set myself up to be in striking distance."
Phelps is entered in four events in the five-day championships, matching his busiest meet since he ended a near two-year retirement in April.
On Friday he'll race the 100m butterfly -- the event he has raced the most since his return -- with the 100m backstroke and 200m individual medley on Saturday and Sunday.
Whether it was the presence of Phelps in the race, or just the quality of the field overall, Adrian and fourth-fastest qualifier Matt Grevers said the pressure was on in the morning.
"There wasn't much room for error," Adrian said, and Grevers added: "People were in the warm-down pool for pretty long -- that's usually a sign they were trying really hard."
Simone Manuel was the top qualifier in the women's 100m free ahead of four-time Olympic gold medalist Missy Franklin with Olympic veteran Natalie Coughlin making it into the final with the eighth-fastest time.
Tyler Clary led the way in the men's 200m butterfly final with a time of 1:56.11 ahead of Chase Kalisz and Kyle Whitaker.
Camille Adams topped the times in the women's 200m fly heats in 2:08.06.
Friday's finals will also include the men's 1,500m free and women's 800m free featuring 17-year-old world record-holder Katie Ledecky.
On June 23 Ledecky sliced 2.86sec off her 800m free world record with a time of 8:11.00 at a meet in Texas.