It was a nostalgic moment for Phelps as he winds down his fourth and final Games here on Saturday.
"This was my last prelim heat ever," he said after coming in second overall to Chad le Clos, the young South African swimmer who grew up idolizing him and won gold to Phelps' silver in Tuesday night's 200-meter butterfly. "So that was pretty fun to do a pretty decent time in it."
Phelps swam his heat in a lane next to Serbian Milorad Cavic, the swimmer he beat by .01 of a second despite his goggles filling with water and blinding him in the 200-meter butterfly race in the Beijing Games.
"We've had some pretty close races in our day," Phelps said dryly. Cavic finished Thursday morning's heat seeded fifth.
Thursday will be busy for Phelps, whose total of 19 medals are the most of any Olympic athlete. Before swimming the 100 fly semifinal tonight, he tries for his 20th medal in the 200-meter individual medley. It will be the second and last face-off between Lochte and Phelps, who enter the final seeded one and three.
"We can guarantee that we're going to race each other, and we're going to race each other hard," Phelps said. "It could be one of the races like at trials where it comes down touch. I know I have to hit every turn well, build momentum. I know last night, going into my breaststroke turn, I was pretty slow. I wasn't using my kick enough."
The race is one Phelps had owned since 2003 when he set a world record in it, but Lochte has made inroads since 2009, when Phelps slackened off from training in the wake of his exhaustion from the exhiliarating Beijing Games. Lochte is the current world champion and record holder, having swam the event in one minute, 54 seconds.
Lochte, though, faces what Phelps called "a tough double" Thursday night, first swimming the 200-meter backstroke final. But Lochte won their first matchup, in the 400 IM that opened the swimming competition Saturday, winning gold while Phelps walked away empty-handed after a fourth-place finish.
Since then, his swims have progressed -- he won silver as part of the 400-meter freestyle relay, another silver in the 200 fly, followed by the gold he won anchoring the 800 free relay that made him the Games' most decorated athlete.
On dry land, the hubbub continues over this latest milestone in his storied career. On Wednesday as he headed to the pool, the phone rang and he heard, "Please hold for the president of the United States."
"I was like, OK !" Phelps said he responded.
"He just got on, and he was saying how everyone was supporting me and behind me at home, and just how proud everybody is of me," Phelps said. "So that was pretty cool.
"And then he finished by saying," Phelps said, "make sure you tell your mom I said hi."