LONDON -- Nick Kyrgios has been criticised for showing his volatile side, but that is precisely what makes him a threat to the world's top players, said Lleyton Hewitt.
The 21-year-old Kyrgios, who faces Andy Murray on Monday for a place in the Wimbledon quarterfinals, drew criticism during the first week of these championships with outbursts at an umpire, reporters and even his own support team.
"He's got to keep his passion, that's the biggest thing," Hewitt told the Press Association on Sunday. "When he is up and about, he's playing his best tennis.
"You don't want to take that flair and flashiness away from him. That's the thing that can make him a top-10 player. Everyone loves different personalities. People want to come to the tennis to watch a guy like Nick play."
Kyrgios apologised Sunday for his latest offensive tirade, after calling a member of his entourage "retarded" during his win over Feliciano Lopez.
But Hewitt, who has been working with his fellow Australian at the All England Club, claimed Kyrgios has the game to threaten world No. 2 Murray on Centre Court
"His ranking is on the right path for sure and he's still only 21 years old," the Australian Davis Cup captain said. "He's got a big game, a lot of firepower and can match it with the best players in the world, and we've seen that before."
Kyrgios was also confident in his ability to pull the upset against his close friend Murray -- who is now the odds-on favourite to win a second Wimbledon title after Novak Djokovic's shocking exit.
"I definitely feel like he's beatable," Kyrgios said. "I rarely walk into a tournament and don't think I can win it."
PA Sport contributed to this report.