WIMBLEDON: Thirty years after their last spellbinding Wimbledon final, Bjorn Borg and John McEnroe are going head-to-head again, and this time, it's serious.

McEnroe unleashed his now famous “You cannot be serious” rant in that 1981 tournament, and the fiery American was tempted to use his trademark phrase again Friday as he revealed he had put his name to an underwear collection entitled “Bjorn Loves John.”

Borg's name has been emblazoned on underwear since 1997, when his brand was launched. Now, he's invited McEnroe on board to collaborate on a collection featuring two designs each, with the pair competing for the most sales.

“I've been wearing his underwear for 10 years,” McEnroe said. “Now I finally have a chance to see if my name has any cache below the waist.”

McEnroe and Borg played each other 16 times in one of the sport's biggest rivalries, including in the finals of Wimbledon and the US Open in 1980 and 1981. It was after his loss to McEnroe in the 1981 US Open final that Borg suddenly walked away from the game at the age of 25.

McEnroe and Borg were eager to talk about their famous rivalry, both on the court and in underwear sales. Borg said the main characteristic he and McEnroe had in common was that “we hate to lose.”

McEnroe added: “Since it's his company and his brand, I feel like my back's against the wall but I was told that I would have an equal opportunity to sell as many as him. This is a two-on-two battle as far as I'm concerned.”