Transcript for London Games 2012: Michael Phelps' Last Olympics?
As we said, michael phelps has one more race tonight, which opens up all sorts of questions about the end of the phelps era and who will replace him. Let's get more from summer sanders, herself a gold medalist. Summer, good morning to you. Good morning. I know. We're saying good-bye to phelps, as he arrived at the games with his phelps-like performance in the 100 butterfly, coming from behind. With 21 medals, can we say he's either the greatest olympic swimmer of all-time or perhaps the greatest olympian of all-time. We were saying he was the greatest olympian of all-time at 19. And I was calling him the greatest olympian of all-time when he won eight gold medals in one olympics games. You add to the four olympics over that tremendous career. And coming back every, single year, with that grueling training. I do think he's the greatest olympian of all-time. So, we're now entering, we hear, the post-phelps era. Is there any chance that the conspiracy theorists might be right and he will come back and follow his mother's advice and swim in the next olympics? I think that's so interesting that debbie phelps has asked her son -- or told her son he should come back for rio. I think this is the end of an era. It's difficult for an athlete to come back and continue the training for four years. It's amazing to see phelps win medals when he said he sort of slacked off in his training over the past few years. That's a reason for him to go and enjoy himself. I guess build a case big enough for what's probably going to be 22 medals at the end of these games. And enjoy being on that side of swimming. I don't think he'll separate himself from swimming. I think he wants to be an ambassador for the sport. He wants to grow it. And he already has. If this is phelps on minimal training, I can only imagine what he would be like with more. Isn't that amazing? Summer, so great to have you. We appreciate it.
This transcript has been automatically generated and may not be 100% accurate.