18-time Olympic gold medallist Michael Phelps lost to rival Ryan Lochte in the 100m butterfly final at the Mesa Grand Prix.
It was Phelps' first final in 20 months. The 28-year-old made his comeback at Mesa, after being last seen in the 2012 London Olympics.
Lochte finished in 51.93sec - second fastest in the world this year, while Phelps finished close behind at 52.13. Kenya's Jason Dunford third in 53.08.
"I swam a final again," Phelps said. "I said I wanted to be around 52.0 and I would be completely happy with that. The race was fun."
Asked if he was eager to continue till the 2016 Rio Olympics, Phelps said he is only focused on enjoying his journey at the moment.
"This is one meet, it's one race," Phelps pointed out. "It's a long way whether I decide to continue or not. I'm doing this because I'm having fun, I'm just enjoying myself on this road, this process, this journey."
Lochte also expressed his happiness to see Phelps back in the race.
"I probably wouldn't have gone that time if Phelps wasn't in there," he said. "I'm glad he's back. Him leaving, it kind of broke my heart a little. Racing against him is so much fun."
Lochte, a five-time Olympic champion who beat compatriot Phelps to win the 400m individual medley at London 2012, said he was tempted to smile during the race, after seeing his longtime friend back.
"Down there at the turn I kind of peeked over and I saw him and almost started smiling," Lochte said.
Phelps jokingly teased: "Why? Because you were ahead?"
Phelps' coach Bob Bowman said it was fantastic to see Phelps in the competitive spirit and that the technicalities can be worked on with time.
"I think that's a really good time to start with," Bowman said. "He hadn't been in a race in two years... his timing was a little off at the start, then he scrambled to catch up, then he missed a whole stroke on the turn.
"My expectations were he would come and maybe enjoy it and not be terrible, so all those were met. That's a really good time to start with."