Michael Phelps notched another impressive performance in his comeback when he won the 100 metres backstroke and beat American rival Ryan Lochte for the second successive night in Athens, Georgia, on Saturday.
Phelps clocked 53.88 seconds, less than a second outside his personal best, while Lochte was a distant runnerup in 54.40.
On Friday, Phelps won the 100m butterfly in 51.67 seconds, the third fastest time in the world this year.
The winner of a record 18 Olympic gold medals, Phelps announced a comeback in April after retiring following the 2012 London Olympics.
The `Bulldog Grand Slam` finishes on Sunday, when Phelps is scheduled to swim the 100m freestyle as he tunes up for the Aug. 6-10 U.S. Championships in Irvine, California ahead of the Pan Pacific Championships on the Gold Coast in Australia.