OMAHA, Neb. — Shortly before the 100-meter butterfly final at the U.S. Olympic swimming trials, Bob Bowman asked Michael Phelps his plan for Saturday night.

“There's no way I'm losing my last race on American soil,” Phelps told his coach of 20 years.

He didn't.

Phelps won in 51 seconds flat, the second-best time of the year, and qualified for a third individual event at the Olympics in Rio de Janeiro.

His legs had not felt strong all week, and he had struggled through an arduous schedule the day before. But even at his lowest points, when he was out of shape or resenting the fact he had to swim at all, Phelps never lost his rare gift for touching the wall first in big races.

It's part of the reason no one is likely to underestimate him when Olympic swimming begins Aug. 6.

Phelps was fourth after 50 meters Saturday night, but as usual swooped past his competition on the second 50 and held off runner-up Tom Shields by two-tenths of a second. Asked whether he expected the 18-time gold medalist to be there at the end, Shields said, “Of course. He's Michael Phelps!”

These trials proved to be a decidedly mixed experience for the greatest swimmer of his generation.

Phelps accomplished what he needed to, qualifying for the Olympics in each of his three individual events. He experienced some profound emotions along the way, choking up after he officially made his fifth straight Olympic team and celebrating his eternal rivalry with Ryan Lochte. He did it all with his fiancee, Nicole Johnson, and their 8-week-old son, Boomer, watching. (Well, Boomer might have been sleeping.)

But from a performance standpoint, this was not one of his best meets, not as good in many ways as his trials of four years ago, when he hated swimming. Despite 18 months of hard training, his legs felt weaker than he wanted. He did not emerge as the fastest man of 2016 in any of his individual events. His times were notably slower than the spectacular results he produced in August in San Antonio.

Phelps has always been a clear-eyed critic of his form in the pool. He has an uncanny grip on the times he needs to win big races. And he knows he'll need to improve over the next four weeks, which will include training stints in Arizona, San Antonio and Atlanta.

“I do understand that I have to swim faster to have a chance to win the gold medal,” he said. “I do know that.”

It did not matter that Phelps, 31, held up better than many of his contemporaries, such as Lochte, Matt Grevers and Natalie Coughlin. He has spent a career judging himself by seemingly impossible standards, and he has taught others to measure him the same way.

He does not want to end his run by conceding Olympic gold to swimmers such as Chad le Clos of South Africa, Laszlo Cseh of Hungary and Kosuke Hagino of Japan, not to mention a potentially healthier Lochte.

Phelps seemed puzzled by some aspects of his week. For example, his taper — the process by which a swimmer ramps down training to rest for a big meet — did not produce the desired results.

“My legs haven't felt like they normally feel during a taper at all, this whole meet,” he said.

Phelps and Bowman have discussed possible tweaks heading into the Olympics, and NBC analyst Rowdy Gaines said it would be foolish to bet against them hitting on the right formula.

“There's no doubt in my mind he's going to be better in five weeks,” Gaines said. “Bob is such a good master of figuring that stuff out, so I think he'll know. In 16 years, how many times have they not figured it out?”

Phelps joked that he'd fire Bowman if he didn't devise a good enough plan.

Going into the trials, Gaines said he'd keep an eye on the details of Phelps' swims, particularly his handling of turns. Well, Phelps gave himself poor grades on that front as well, and said he can't afford such sloppiness in Rio.

“I think there are a lot of small things that Bob and I can do to get there,” he said. “If you look at any of my turns in the IM, they were all awful, and it's a lot of small things.”

Phelps also learned exactly how much his body has changed with age when he swam three races Friday, including two — the 200 IM final and the 100 butterfly semifinal — within a 30-minute span.

He was tired enough that he qualified just sixth in the 100 butterfly, an event in which he's won three straight Olympic gold medals.

He appeared to be in agony just walking down the stairs after the third race, a fact he confirmed between gulps of air during his postrace interview. Phelps later noted that tests showed an extraordinary level of lactate in his blood in the moments immediately after the race, meaning he was unusually low on oxygen.

He sucked down a protein drink and two energy bars, spent 40 minutes in the warm-down pool and sat in a 50-degree ice bath to recover.

Phelps simply has not dealt with such strenuous racing days over the past four years. But he will face a near-identical triple Aug. 11 in Rio. And the competition to qualify for the 100 butterfly final will be tougher there.

He will also likely mix in the 400-meter medley relay and possibly one of the freestyle relays. So, even if his schedule won't be as full as in the past, he'll have plenty to do.

As Phelps pointed out, his body has not always delivered the expected results since he returned to competition in April 2014 after a brief retirement. But he said he trusts that he and Bowman have done the right work to prime him for a last glorious meet in Brazil.

“There have been a lot of frustrations in meets that I've had over the last two years, and maybe this is just one of them,” he said. “You know, being able to get on the team and being able to have the chance to improve over the next couple of weeks ... I think it's going to be good.”

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