Three-time winner Greg LeMond believes Lance Armstrong was only capable of a top-30 Tour de France finish "at best" without performance-enhancing drugs.
LeMond, 52, is the only American winner of the Tour after Armstrong was stripped of his seven titles in 2012 for systematic doping.
"If he was clean and everybody else was clean, he's a top-30 [Tour finisher] at best," LeMond told CNN.
"He's not capable of winning the Tour, he's not capable of the top five."
Armstrong, 42, was also banned for life following a United States Anti-Doping Agency investigation into the doping practices of the United States Postal Service team, a punishment LeMond feels is fair.
"There are people who are criminals who just shouldn't be able to participate again in anything," he said.
"It's like [jailed financier] Bernie Madoff - should he be allowed to come in and be a part of Wall Street managing money? No, he shouldn't.
"And that's [the case] with Armstrong. He shouldn't be allowed to be back in sport."