Australia's Ian Thorpe shows off his gold medal following the 400m mens freestyle swimming event at the Sydney 2000 Olympic Games September 16, 2000. Thorpe set a new world record time of three minutes 40.59 seconds.
Thorpe, who failed in his comeback bid to make the London Games, said he was confident Magnussen could smash Brazilian
Cesar Cielo's 46.91-second 100m freestyle world record as early as the semi-finals.
"For me, watching him, I see a new era of sprinting," Thorpe told Australian media on Friday.
"He's the most impressive swimmer I've seen, probably over the past decade, that's new to the sport. He's exciting to watch."
Thorpe, who missed out on a place in the Australian team after failing to qualify in the 100m and 200m freestyle events, said that Magnussen was leading the country to "the dawn of a new era in swimming".
"I think he will do incredible things. I think you could see an amazing result in the (100m freestyle) semi-final and then in the final. Obviously I think he's going to win."
Having won five gold medals at the Sydney and Athens Olympics, Thorpe is Australia's greatest Olympian, but he believes Magnussen could take the title from him.
"I'd like him to. Why not?," he said.
"I wouldn't mind seeing him swim a 200 as well -- I think he can. It's a good possibility."