And make no mistake. This is more than mere hype. This really is as perfect a rivalry as the sport allows. Phelps owned the Beijing Games, winning a record eight gold medals. Lochte won a total of four medals in 2008, two gold and two bronze. He has steadily improved since then.
So what we have is a sporting immortal, Phelps, vulnerable to a human - albeit a superbly talented one.
"We're all excited about that race," three-time Olympian Natalie Coughlin said. "I think it's going to have a lot of energy behind it, and hopefully it will give us all a lot of momentum going into the next eight days."
The U.S. team had its pre-Games news conference Thursday afternoon. A large auditorium was packed as Phelps sat onstage and took questions for 30 minutes. When he was done, a handful of teammates, including Lochte, came out and took their collective turn.
That was a practical decision - as Coughlin said, otherwise Phelps gets all the questions while his teammates doze off - but it accurately depicted reality. Coughlin has a drawer full of medals. Lochte and Rebecca Soni are Olympic champions. They are all great swimmers.
Phelps is Phelps.
Lochte may be able to defeat him in a head-to-head match. He'll get two chances, Saturday's 400 IM and the 200 IM, which will be raced Wednesday and Thursday. But no matter what happens, Lochte can only be measured against the enormous scale of Phelps' accomplishments. Lochte can win a battle or two, but the war was over a long time ago.
So what's going to happen?
Lochte would appear to have two advantages: momentum and motivation. His star is ascendant while Phelps, at 27, is admittedly feeling a little older and a little less resilient than he did in Beijing. This first race is one he swore off a number of times because it is so demanding.
"It is going to be a lot more painful than last time," Phelps said. "I can tell you that much. I've found that recovery is a lot more important now than it was then. Everything [in Beijing] was like perfect. Everything was right in place."
Since Beijing, Phelps has admitted losing his competitive edge. He'd done what no one else ever had. Anything he did after that would be anticlimactic. He was smart to drop an event, to compete in seven races this time and tamp down the pressure to repeat himself.
Phelps' diminished focus provided Lochte his opening. And he really is as good a swimmer right now as there is in the world. It would really be fun if he could go back in time to the Water Cube in 2008 and race Phelps at his peak. This will have to do.
Lochte and Phelps have handled this whole thing with good grace and class. Lochte is impossible to dislike. He's as open and chatty as Phelps is measured and reserved. Even as he talks about facing everyone in the pool, not just Phelps, you can feel how much he's burning to stand on the top of the medal podium Saturday night. It would mean everything.
Would it mean everything to Phelps? That, as much as anything, could be the deciding factor here.
Phelps didn't win eight gold medals because he fell in the pool and didn't sink. There is a fierce work ethic, an immense competitive spirit, and a bottomless supply of pride. He couldn't have liked losing in the trials, but this is different. This is his domain, the Olympic Games.
He seemed to have a little edge back Thursday. When the moderator tried to skip over a question about teammate Tyler Clary, who told a newspaper that Phelps had a poor work ethic, Phelps leaned forward and insisted upon answering. He wasn't exactly happy about it.
And when asked about Lochte's notorious workout routine - which includes strongman training like throwing truck tires - Phelps chuckled.
"I don't see myself throwing tires," he said.
When these Games are over, Phelps will have the most medals in Olympic history. He will be in every conversation about the greatest athletes of all time.
That will be true even if he loses a race or two to Ryan Lochte. The feeling here is that he won't.
Contact Phil Sheridan at 215-854-2844 or firstname.lastname@example.org, or follow on Twitter @Sheridanscribe. Read his blog, "Philabuster," at www.philly.com/philabuster. Read his columns at www.philly.com/philsheridan