MELBOURNE (Reuters) - Australia's bad boys of tennis Nick Kyrgios and Bernard Tomic have been named in the Davis Cup squad for the World Group playoff against Slovakia after bowing out of the U.S. Open in typical controversy.

Team captain Lleyton Hewitt named the combustible pair in a six-man squad which will be reduced to four for the Sept. 16-18 grass-court tie at Sydney's Ken Rosewall Arena.

World number 19 Tomic was dumped out of the first round at Flushing Meadows by 72nd ranked Bosnian Damir Dzumhur and slapped with a $10,000 fine for firing lewd comments at a heckler in the crowd.

Kyrgios, ranked 16 in the world, retired hurt when trailing in his third round match against Ukraine's Illya Marchenko, earning a stinging rebuke from four-times champion John McEnroe who challenged the 21-year-old to quit the sport if his heart wasn't in it.

Hewitt on Monday said Kyrgios was a doubt for the tie but would be given every chance to recover from a hip injury.

A day later, the former world number one said in a media release: "... all the boys are fired up and ready to go out and get the win for Australia."

Kyrgios was a late withdrawal from the World Group first round tie against the United States in Melbourne in March, which caused a rift with Tomic who played in the 3-1 defeat to the visitors.

Tomic publicly questioned Kyrgios's pull-out due to a 'flu-like illness', prompting Kyrgios to fire back on Twitter: 'Just don't expect me to have your back anytime soon."

Kyrgios's withdrawal from the U.S. Open continued to rumble on Monday, with high-profile Australian coach Roger Rasheed questioning why he had played doubles at Flushing Meadows if carrying an injury.

Rasheed suggested Kyrgios's lack of a coach was costing him.

"A coach would definitely stream all that back. Strip it all back and really make it quite simplistic for him," the outspoken 47-year-old told Sky Sports.

Kyrgios gave Rasheed's comments short shrift.

"John McEnroe takes a stab, I understand," he tweeted on Tuesday. "Roger Rasheed haha maybe not so much. I got to ur career high when I was 18... ease up champ."

(Reporting by Ian Ransom; Editing by Amlan Chakraborty)