Former world heavyweight champion Lennox Lewis says fellow Briton Amir Khan would give Floyd Mayweather or Manny Pacquiao "trouble" if he fought them.
Mayweather will fight Pacquiao in May and Khan is keen to line up a fight with either of them in the future.
"I think Khan has been looking great lately," said Lewis.
"His speed is a factor they would find difficult to contend with. Khan would give them trouble."
Khan says he in in talks with both the Mayweather and Pacquiao camps but for now is targeting a fight with Miguel Cotto, Timothy Bradley or Juan Manuel Marquez.
"The next fight is likely to be in America again and it's all about keeping my name high over there and hopefully one day getting that big fight against Mayweather or Manny Pacquiao," Khan told 5 live on Saturday.
Biggest fight in history?
The Las Vegas fight between welterweights Mayweather and Pacquiao - with the American's WBC and WBA titles and Filipino Pacquiao's WBO title on the line - promises to be the richest bout in the history of boxing and generate as much as £162m ($250m).
Asked whether the fight between the pair, widely regarded as the best boxers of their generation, was the biggest in history, Lewis, 49, told BBC Radio 5 live's Sportsweek he regarded it as a "super-fight".
"Look at [the fights between] Sugar Ray Leonard, Thomas Hearns, Marvin Hagler - there are a lot of super-fights.
"If I came out of retirement now and boxed Wladimir Klitschko I'm sure we'd make more money because we're heavyweights and command a lot more attention. People love heavyweights."
Mayweather or Pacquiao?
Asked who he tipped to win, Lewis, who beat Evander Holyfield and Mike Tyson as well as Klitschko before retiring in 2004, continued: "Floyd is the best at side-stepping and movement and he's very quick and hard to hit. Pacquiao is a great guy when it comes to offence and trying to break a person down - he's trying to knock you out, so it's a great match-up between styles.
"I think Floyd has so much talent and quickness, that natural ability to win. It really depends on his heart. Pacquiao has a lot of heart.
"It's difficult but I think Mayweather has all the advantages, that natural ability and rhythm. Pacquiao, you never really know how he's going to come out because he's boxed differently on different occasions with different opponents."
On coming out of retirement
"I have dreamt about it - then woken up and talked myself out of it," said Lewis, who won super heavyweight gold for Canada at the 1988 Olympics before embarking on his 44-fight pro career.
"My friend Razor Ruddock is coming back at 51. His last fight was 14 years ago and he's making a mistake. I don't think it's necessary to come back at this point."