Michael Phelps and Ryan Lochte's friendly rivalry

Michael Phelps and Ryan Lochte will face off in Thursday night in Rio in what could be their final showdown. Their rivalry spans 12 years, but simply calling them rivals is only half the story, reports CBS News correspondent Ben Tracy.

Lochte has won four consecutive world championships in the grueling 200-meter individual medley race, but never Olympic gold. Phelps beat him in Athens, Beijing and London.

"The competitive environment between those two guys has always been good," said Gregg Troy, who coached both swimmers at the 2012 Olympics. "Even at their own testament, they both say they bring out the best in each other. And I think there's a mutual respect, but also they're very competitive and neither one wants to give in or go home."

Phelps made his Olympic debut in Sydney in 2000 at just 15. Lochte showed up four years later in Athens, and ever since, has had to swim in the shadow of the most triumphant Olympian ever.

If it weren't for Phelps and his 25 medals, Lochte would be the most decorated male Olympic swimmer of all time. He's won 12 medals, one more than Mark Spitz, the star of the 1972 games.

"He's the hardest competitor I've ever had to go up against and he's not likely to back down. And I'm not either," Lochte said.

But at the U.S. Olympic swim trials this summer, Phelps said their relationship has evolved.

"Honestly, I think we've both just grown up. I do feel like I talk to him more and joke around with him more than I really did in the past," Phelps said.

Dara Torres also won 12 medals for Team USA and knows both Phelps and Lochte. She said they make each other better.

"I don't think we'd be as good as they are in this event if they didn't push each other," Torres said.

"Are they more competitors or is this more of a bromance?" Tracy asked.

"You can tell that they are really good friends, but once they get on those starting blocks, they're not friends anymore," Torres said.

Because at the end of the race, someone has to touch the wall first.

"Even if this is our last go-round together, we will definitely make it count," Lochte said.

Michael Phelps has said he will retire after Rio, so Thursday night's match could be the end of an era. But Lochte said he's not buying it and believes Phelps will be back for more.

The two are rooming together in the athletes' village, so perhaps he has the inside scoop