When pressed further about his plans, he didn't budge from his conditional tone.
"I'm not saying yes or no yet," he said. "I'm doing this because I want to, and I'm doing it because I'm having fun. I'm not putting any pressure on myself to say I'm doing this or say I'm doing that in the future. I'm just enjoying myself right now and this road and this process, this journey."
It's not clear what's next for Phelps. His longtime coach, Bob Bowman, indicated he might swim another short program May 15-18 at the Charlotte Grand Prix. His performance in Mesa qualified him to swim at the U.S. Nationals in August, but he hasn't committed to that meet.
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Neither swimmer nor coach was thrilled with Thursday night's 100-meter butterfly final. Phelps used the butterfly in Friday's 50-meter freestyle in part because he's still seeking his old rhythm.
But even a detail maven such as Bowman was able to step back and appreciate the greater experience of Phelps' return.
"It's fun to have him here," he said. "… I just think having him back in the sport is great. As long as he's enjoying it like he is, it's good for everybody."
Phelps can hardly escape reminders of his influence on younger swimmers. He's the self-professed grandpa of the star-studded team at North Baltimore Aquatic Club. In Mesa, he met 15-year-old phenom Michael Andrew, regarded by many as the eventual heir to Phelps' throne.
Andrew, a Kansas native, fired off several star-struck tweets about the encounter. "Swimming needs you!" he said in one. "So excited to race the GOAT [greatest of all time] this week!!!" he enthused in another.
Andrew didn't swim a fast enough qualifying time to set up a meeting with Phelps in the 100-meter butterfly. But he watched from the deck as his idol returned to competition.
Justin Lynch, 17, did get to swim against Phelps in the butterfly final. "It's a whole other level racing against the best in the world," he said.
Yet no one seemed more excited about Phelps' return than his old rival, Ryan Lochte, who won their Thursday duel in the 100-meter butterfly.
"I probably wouldn't have gone that time if Phelps wasn't in that pool with me," Lochte said. "Racing against him is so much fun. It's a challenge. And now that he's back, I've got a big, old smile on my face."
Lochte spoke with uncommon emotion of renewing his competitive friendship with Phelps, whom he hadn't seen since the London Olympics. He even said his rival's retirement "broke my heart a little."
Asked his reaction to Lochte's comments, Phelps seemed a bit taken aback. Perhaps he's still getting used to the impact of his return, even if he's always held ambitions to change his sport.
"I've said this my whole career and I'll continue to say it: This sport has given me so much and I don't think I can do enough to give back," he said. "This has been an amazing journey I've gone on so far, and I just hope it continues."