Rowdy Gaines had a simple message after calling Michael Phelps' 18th and last gold medal-winning race Saturday. "All I can say is thank you," the NBC swimming analyst said.

The curtain officially closed on the Phelps era with his final medley relay race and 22nd Olympic medal. The swimmer said he's retiring after London and has looked like it, appearing relaxed and reflective in interviews. Gaines and partner Dan Hicks have covered Phelps in four of the five Olympics where they have been partners for NBC.

"I thank God every day that we had him in our sport and nobody else had him in theirs," Gaines said in an interview.

NBC will miss him, too. The network announced that it would air a retrospective on Phelps' career Sunday at 7 p.m. EDT and PDT, featuring Bob Costas' lengthy interview with the swimmer. "Michael Phelps: America's Golden Champion" will last an hour.

Hicks understood the historical perspective in calling the race Saturday. "Sooner or later you have to say goodbye to the sports greats," he said.

Gaines, himself a three-time gold medal-winning swimmer, said Phelps has clearly done more for swimming than anyone else in its history.

They've had a friendly relationship, although Phelps appears to have used some of Gaines' words as motivation. While calling a race in 2003, Gaines suggested that Phelps had started off too quickly and wouldn't be able to maintain his pace. Phelps won, setting a world record for time in the process.

After many of his subsequent wins, as recently as last year, Phelps would needle Gaines: "Did I fade in that race, Rowdy?"

When Phelps lost his first final of the London Olympics to Ryan Lochte, Gaines was blunt in his assessment that Phelps had not properly trained for the event. Gaines didn't consider that criticism because Phelps himself had admitted the same thing.

Gaines questions whether Phelps will, or should, retire from swimming after London.

"He doesn't have to have a job," he said. "It's not like he has to go to work as a banker to make money. He can live off being Michael Phelps."

He'd advise Phelps to take a couple of years off and then see how he feels. Phelps would still be young enough to be competitive in the 2016 Games, and there would be no pressure, he said. "Maybe it's just wishful thinking," he said.

There's already speculation that Phelps, poised and comfortable on camera, could head into broadcasting.

Could he wind up taking Gaines' job some day? Continued...