Curiosity will be the theme of the Hopman Cup this summer as Roger Federer and Nick Kyrgios return to the tennis world stage following vastly different stints on the sidelines.

Federer is one of the most admired players in world tennis.

His sublime skills and affable personality have made him a fan favourite wherever he’s played.

With 17 grand slams to his name, Federer is already considered tennis royalty.

But after spending the past six months on the sidelines following knee surgery, Federer admits he’ll be entering the unknown this summer.

Kyrgios has joined Federer as one of the most watched players on tour – but for hugely different reasons.

The brash 21-year-old is equal-parts racket-wielding magician and explosive bad boy, who just four years into his professional career has a rap sheet that is bursting at the seams.

From explosive arguments with line judges and chair umpires, to sledging an opponent about his girlfriend’s sexual activities – Kyrgios has become a walking headline.

Arguably his most serious offence came in October, when he deliberately threw a series of points in a shock straight-sets loss to German journeyman Mischa Zverev at the Shanghai Masters.

Kyrgios was banned from the tour and ordered to undergo counselling as punishment for that display.

And now after serving his penance, he is ready to return to the court, and will do so in what is epxpected to be a supportive home crowd in Perth.

Kyrgios well and truly won over the Perth fans last year when he teamed with Daria Gavrilova to end Australia’s 17-year Hopman Cup title drought.

The pair will join forces once again, but the Swiss duo of Federer and former world No.7 Belinda Bencic will start as favourites.

Federer has appeared at the Hopman Cup twice before.

He won the event at the age of 19 in 2001 with Martina Hingis, before teaming up with his now wife Mirka in 2002.

Federer will use the 2017 edition to get rid of any rust acquired in his time away from the court.

Bencic is also hoping to use the Hopman Cup as a springboard to better things following an injury-interrupted year.

The 19-year-old rose to No.7 in the world after storming into the fourth round of the Australian Open and reaching a final in Russia before back and wrist issues ruined the rest of her year.

The Hopman Cup was dealt an early injury blow when two-time Wimbledon champion Petra Kvitova was forced to withdraw with a foot injury.

A day later, Kvitova was rushed to hospital after her hand was cut by a knife-wielding intruder at her apartment south of Prague.

Her withdrawal from the Hopman Cup left the women’s field light on for talent.

But the men’s field is bristling with firepower.

Federer and Kyrgios are the headline acts, but Frenchman Richard Gasquet, rising German star Alexander Zverev, and American Jack Sock will also command plenty of attention.

The dream final would be Australia against Switzerland, which would see Federer and Kyrgios lock horns at a sold-out Perth Arena.