INDIANAPOLIS — Nathan Adrian felt a little strange walking around the pool during the U.S. National Championships.

Michael Phelps wasn’t there last week. Ryan Lochte was missing, too. And for the first time in almost two decades, when the American long-course world championship team was announced, neither of its biggest stars appeared.

“It’s weird, really weird,” Adrian said. “I’d been focused on swimming for so long, and then it was about swimming fast and then it was like you’re a veteran and then you look at it now and it’s like you’re one of the leaders of the team. It feels like it was only a few years ago I was nipping on the heels of Jason Lezak.”

Actually, it was eight years ago that Adrian captured his first national title.

But things change, and the search for new American leadership is starting all over again.

From Mark Spitz and John Naber in the 1970s to Matt Biondi and Rowdy Gaines in the 1980s, this changing of the guard has become relatively routine and virtually seamless. This time, it will be a more dramatic transition.

Phelps qualified for his first Olympics as a gangly teenager in 2000. From the point on, he, Lochte or both have represented the U.S. at every Olympics or long-course world championship team through the Rio Games last summer. Adrian was right there with them, at all those international meets since 2009.

So with Phelps retired and Lochte suspended, Adrian is in line to become the next face of the U.S. men’s team.

“He was a leader in Rio and I think he’ll be the leader till he’s done,” 20-year-old Townley Haas said.

It won’t be easy, but nobody is more qualified right now than the 28-year-old Washington native.

He owns five Olympic gold medals, has a smile that shines as brightly as any of them and a charisma that has made him one of the most popular swimmers. He apprenticed under Phelps and Lochte and, yes, even Lezak. A year ago, he was one of three captains on the men’s Olympic team. Today, he’s the only one heading to Budapest, Hungary.

The truth is, Adrian can’t do it alone.

“Those two are very big personalities,” said U.S. men’s coach David Durden, who also coaches college powerhouse California. “You’re not going to fill that void of Michael Phelps, for sure. We’re trying to get him back in the water for 2020. But we don’t need someone to be a Michael Phelps. We need them to be themselves and that’s something we’ll work on. We’ll miss Ryan, as well, because he’s that versatile guy who keeps it really light. We’ll miss that personality and want it back in 2018.”

Adrian has plenty of teammates who can help.

Some, like 32-year-old Matt Grevers, have been around. The four-time Olympic gold medalist rebounded from a crushing 2016 Olympic Trials to reclaim his spot on the U.S. team with a win in the 100-meter backstroke.

Others, like 22-year-old Ryan Murphy, are still carving out their place. The world-record holder in the 100 back and a three-time Olympic gold medalist in Rio de Janeiro, qualified in the 100 and 200 back despite a less-than-stellar performance.

After taking home Olympic silver in the 400 individual medley last year, 23-year-old Chase Kalisz will compete in the 200 and 400 IMs at the worlds.

But the man to watch may be 20-year-old Florida native Caeleb Dressel.

He won two golds on relay teams in Rio, both in relays and now embarks on an ambitious schedule from July 23-30. He qualified in six events — the 50 and 100 butterfly, the 50 and 100 freestyle and the 400 and 800 free relay.

“It’s incredible,” Adrian said when asked about Dressel’s feat. “But that’s a really grueling schedule at worlds.”

If Dressel can even come close to duplicating that feat in Budapest, Durden could have the perfect blend .

Up-and-coming stars like Dressel would have three more years to grow into their new roles.

And Adrian, the veteran who is still on top of his game and plans to stick around at least through the 2020 Olympics, will provide the veteran voice.

“I’d certainly take ownership of it,” Adrian said. “I’ve been blessed to have older athletes take care of me, so I know a thing or two about it and if that’s what it takes, I’m happy to do it.”