Phelps bested by Shields in 100m fly
Michael Phelps, pictured after winning his heat in the men's 100m butterfly preliminaries, during the 2014 Phillips 66 National Championships, at the Woollett Aquatic Center in Irvine, California, on August 8, 2014 - by Harry How
Tom Shields on Friday edged Phelps by one one-hundredth of a second, taking the gold in 51.29sec to Phelps's 51.30.
It was a disappointment for Phelps, the 18-time Olympic gold medalist who had clocked the fastest time in the world this year in the morning heats of 51.17sec.
The 29-year-old is swimming just his fourth meet since ending a near two-year retirement in April.
The runner-up finish was likely good enough to book Phelps's first spot in a major international competition since the London Games.
The meet is the qualifier for the Pan Pacific Championships in Gold Coast, Australia, from August 21-25, the biggest international meet for US swimmers this year.
Results from this week and the PanPacs will determine the US team for the 2015 World Championships in Russia, a key stepping stone on the road to the 2016 Rio Olympics.
While Phelps couldn't match his blistering preliminary swim, his performance was a big improvement on his first final of the week -- a seventh-placed finish in the 100m free on Wednesday.