Irvine - Olympic swim king Michael Phelps and reigning Swimmer of the Year Ryan Lochte will wage a series of duels at this week's star-studded US national championships in Irvine, California.
Phelps, who has competed in four meets since coming out of retirement in April, will face the toughest test of his comeback as he is entered in the 100m freestyle, 100m butterfly, 100m backstroke and 200m individual medley.
"The 100 fly feels the best," Phelps, who retired after the 2012 London Games, told reporters on the eve of the August 6-10 nationals. "It's what I've raced the most since I came back."
The national championships will serve as a qualifier for the August 21-24 Pan Pac Championships at the Gold Coast in Australia which will be used to determine the US squad for next year's World Championships in Russia.
Phelps, the all-time Olympic leader with 18 gold medals and 22 medals overall, said he had grown restless and out of shape during retirement. He eventually got in touch with longtime coach Bob Bowman and set in motion his comeback.
"Retirement was pretty boring, to be honest," Phelps, 29, said.
Competition at the nationals should be anything but boring, as Phelps is expected to face rival Lochte, a five-time Olympic champion, in each of his events.
Lochte, also on the comeback trail after tearing ligaments in his knee last November and then re-injuring it, will be even busier as his schedule also includes the 200m freestyle and 200m backstroke.
The women's side also features scintillating showdowns of Olympic champions and the busiest swimmer of them all in 17-year-old Katie Ledecky, who will go against gold medallists Missy Franklin and Allison Schmitt.
Ledecky, who as a 15-year-old won the 800m freestyle at the London Games, has entered eight events, including every freestyle race from 50m through 1 500m.
Franklin, who burst to prominence in London with four golds and a bronze, and Schmitt will compete against Ledecky in the 100m and 200m free, while Schmitt is also entered in the 400m freestyle.
The 19-year-old Franklin will also contest the 100m and 200m backstroke, which she swept at the London Games.
Five-time Olympic champion Lochte joked that Phelps must have grown tired of or frustrated by his infatuation with golf.
"Probably his golf isn't going so well," joked Lochte about Phelps ending his retirement. "Bottom line, I'm glad he's back. It's great for the sport."