KAZAN, Russia (AP) Hungarian veteran Laszlo Cseh has set the year's best time in the 100-meter butterfly - and Michael Phelps will surely take notice when he competes half a world away this week.
Cseh touched in 50.91 seconds to lead the preliminary heats at the swimming world championships on Friday; beating his personal best by half a second.
''It just slipped out,'' Cseh said. ''When I saw the time I thought, `Jesus Christ, under 51 in the morning? No way.' ... It was a good start, and then in the second 50 I pushed because you have to push anyway.''
Tom Shields of the U.S. qualified second in 51.09, while Chad Le Clos, the South African who took silver behind Phelps in this event at the 2012 London Olympics, advanced in only eighth in 51.83.
Cseh will get a chance to go even faster in the semifinals later Friday, and then in Saturday's final.
Phelps' world record of 49.82 was set in 2009 in a now-banned rubberized suit.
Phelps is racing the 100 fly, his best event, this week at the U.S. championships in San Antonio. He's missing the worlds after being suspended by USA Swimming for a second drunk-driving arrest.
Having toiled for years in Phelps' shadow - he took three silvers when Phelps won a record eight golds at the 2008 Beijing Olympics - Cseh is showing newfound sprinting speed at the age of 29.
Recently reunited with his childhood coach, the good-natured Cseh has already taken gold in the 200 fly, edging the favored Le Clos, and bronze in the 50 this week.
On a day for veterans, 35-year-old Grant Hackett led off as Australia beat the U.S. by 0.15 to top the 4x200 freestyle relay heats.
A three-time Olympic gold medalist, Hackett came out of retirement last year after six years out. His leadoff leg was 0.38 faster than that of the 20-year-old American Reed Malone - although not the fastest overall.
''It was a good heat swim for me to get to a 1:47 but obviously not fast enough (for me) to get to the final tonight which was unfortunate,'' Hackett said. ''I'm not 100 percent sure (to be out of the final) but pretty confident going with the times at this stage.
''I produced a 1:49 in my first heat swim at nationals so to go 1:47 off the gun after waiting around for a few days is actually really good for me. I don't naturally have that easy sprint, so it's always hard getting up in a 200.''
Aiming for her fifth gold of the meet, U.S. teenager Katie Ledecky led the 800 freestyle heats in 8:19.42.
Ledecky was under world record pace for the first 300 meters but finished well off her own mark of 8:11.00 set last year.
In the 50 free, Olympic champion Florent Manaudou of France swam 21.71, edging American contender Nathan Adrian by 0.02.
With three-time defending champion Cesar Cielo having withdrawn from the championships due to a left shoulder issue, Kristian Gkolomeev of Greece qualified third in 21.87.
Fresh off his disqualification in the 100, Russia's Vladimir Morozov advanced fourth in the single-lap splash and dash, while Bruno Fratus of Brazil was fifth.
Ning Zetao of China, crowned the 100 champion a night earlier, barely made the semifinals in 14th, as did 2001 champion Anthony Ervin of the U.S. in 15th.
Aiming for her second gold of the meet, Sweden's Sarah Sjostrom topped the 50 fly heats in 25.43. Alzain Tareq, a 10-year-old from Bahrain, finished last, 41.13 seconds behind.
Katinka Hosszu, Hungary's ''Iron Lady,'' topped the 200 backstroke in 2:07.17, while Olympic gold medalist and two-time defending champion Missy Franklin qualified second in 2:07.84.
Franklin is still seeking her first individual gold of the meet.
''It felt so good. It's always so hard waiting until Day 6 because it's my favorite event,'' Franklin said. ''I was hoping for a 2:08, so 2:07 I was really, really happy with.''
Andrew Dampf can be followed at www.twitter.com/asdampf