Michael Phelps has set his sights on a 20th gold medal by posting the second-fastest time in the semifinals of the 200-meter butterfly.
Phelps went out strong in Monday night's race, and then backed off a bit in the final 50 to save his energy for Tuesday's final.
Hungary's Tamas Kenderesi surged to the wall first in 1 minute, 53.96 seconds.
Phelps was next at 1:54.12, followed by Hungary's Laszlo Cseh and South African Chad le Clos, the defending Olympic champion.
Four years ago, Le Clos pulled off one of the greatest Olympic upsets when he beat Phelps, who had the lead but glided too long on his finish.
Now, it's time for the rematch.