Nick Kyrgios during his win against Fillipo Baldi.

Nick Kyrgios during his win against Fillipo Baldi. Photo: Wayne Taylor

He's up against a great mate in the biggest match of his career, but Nick Kyrgios' former coach has warned him not to let it curb his fiery on-court nature in Saturday's Australian Open junior singles final.

Canberra product Kyrgios will play doubles partner Thanasi Kokkinakis for his first junior grand slam title after both won their semi finals on Friday.

Third seed Kyrgios, officially the world's No. 1 junior, needed only 41 minutes to thrash Italian eighth seed Filippo Baldi 6-2, 6-1, while Kokkinakis was almost as dominant in his 6-3, 6-2 defeat of Croatian Borna Coric.

Kyrgios' old mentor Todd Larkham conceded that the 17-year-old would prefer not to play a close friend in such a big match.

''Playing against a mate, to be honest with you as a player you wish you weren't playing them in such a big game,'' Larkham said.

''It's difficult sometimes, you don't know how fired up you should get after winning a big point, you can be a little subdued in that respect.

''Nick relies on really getting pumped up and fired up, that's when he plays his best tennis.

''He's got to still do that. If he wins a big point, he has to do the big 'come on' and get the crowd involved.''

Larkham said Kyrgios thrives under big-match pressure and has already proven as much by winning the Wimbledon and French Open junior doubles titles last year.

''He's played two finals and won both, he can really draw on that,'' Larkham said.

''He's doesn't lack confidence but he needs motivation and whenever he gets into a big match that motivates him big time.

''Nick seems to need that big match to really motivate him to play his best tennis.''

As well as their doubles association Kyrgios and Kokkinakis are regular practice partners, and know each other's games inside out.

Larkham said Kyrgios and his coach for the past year, Des Tyson, would have an element of surprise in store to overcome that familiarity.

Kyrgios overcame Kokkinakis 6-3, 7-5 in the Australian 18-and-under final at Melbourne Park in December.

''You've got to keep something up your sleeve, something you haven't done against someone you've played or practised with so often,'' Larkham said.

''He'll have something ready that Thanasi isn't expecting for sure.

''I think walking out there with a mate, it does take those nerves out of it a little bit, definitely.

''He's a big-match player Nick, and any time he's been put in this type of situation he's risen to it.

''I'd expect him to shake the nerves pretty quickly and really get stuck into it.''

Kyrgios said the key to his victory over Baldi was the variation of his serve.

''I served spectacular today, I mixed my spots up well, which is what I thought I had to do, because he's a dangerous player when he gets into his rhythm,'' Kyrgios said.

''It's a great bit of history with two Australians in the final, it hasn't been done for a long time.''

The last all-Australian boys' final at Melbourne Park was in 1994 when Ben Ellwood beat Andrew Ilie in three sets.

SATURDAY

Australian Open boys singles final: 3-Nick Kyrgios (AUS) v Thanasi Kokkinakis (AUS), after completion of girls singles final which begins at 1pm. TV Time: Live on 7Two from 2.30pm.