Australia’s Nick Kyrgios stirred a controversy of sorts when he used an underarm serve during his Mexico Open win against Rafael Nadal on Thursday, but tennis legend Roger Federer doesn’t see anything wrong in the use of such a tactic.

Speaking to the press after his straight-sets quarter-final victory against Marton Fucsovics at the Dubai Championship on Thursday, Federer said players shouldn’t be ashamed of using the underarm serve.

Kyrgios has been slammed on social media for his style of play against Nadal at Acapulco, prompting the 23-year-old to defend himself. “I mean isn’t the idea to serve where the person can’t get the ball? Try to get an ace?” he wrote on Facebook.

Nadal came out strongly against Kyrgios after their match on Thursday, in which the latter called the trainer twice, used expletives for fans in the stadium, apart from serving underarm.

All these things didn’t go down well with Nadal, a 17-time Grand Slam champion, who said that Kyrgios “lacks respect for the public, the opponent and himself.”

Federer didn’t comment on Kyrgios’s on-court behaviour, but reckoned it is all right for a player to use an underarm serve. “Especially when guys are hugging the fence in the back. From that standpoint (players) shouldn’t be ashamed to try it out,” the 20-time Major winner was quoted as saying by foxsports.com.au.

“You just look silly if you miss it sometimes. But why not try it? The problem is in practice, you never really try it. When you come out in the big stage in front of a full crowd, [it is] tricky to pull off.”