Olympic legend vows to buckle down after weak finish at US Championships

Michael Phelps, the most decorated Olympian in history, didn't return to competitive swimming to finish sixth.

"I hate this," Phelps said after slogging his way to sixth in the 100m backstroke at the US Championships on Saturday.

Even though the 100m back was never one of the events that featured in his epic Olympic campaigns, and knowing he was lacking a solid training base after a near two-year layoff, Phelps was clearly stung.

But with the Pan Pacific Championships - his first international meet since the London Olympics - looming in two weeks and the world championships on the horizon in 2015, Phelps was anything but discouraged.

Instead, he said he was ready to buckle down.

"Anything to be able to change this," he said. "I'm not going to use the excuse of taking off a year and a half to two years.

"When there are workouts, I need to be at every one."

Phelps booked his berth for the PanPacs in Australia with a runner-up finish in the 100m butterfly on Friday.

He had looked like a world-beater when he posted the fastest time in the world this year in the fly heats, a race coach Bob Bowman called his best "by far" since returning to competition.

But Phelps delivered a flawed effort in the final to take silver behind Tom Shields.

His swim in the final of the 100m free was even worse, a botched turn leaving him in seventh place.

"I guess that's one thing I have had trouble with," the once unflappable superstar said of his unease in the finals.

With his PanPacs berth confirmed, Phelps wasn't sure he'd swim his last scheduled race on Sunday, the 200m individual medley.

His 18 Olympic gold medals include three 200 IM triumphs, but he didn't sound as if he was counting himself a real contender.

And he wasn't sure if Bowman would want him to get another race under his belt or return to training.

"I would assume he wants me to race because I haven't done that many 200s this year," Phelps said.

"If only just to see whatever might happen."