Melbourne - World number one Serena Williams dispelled concerns she was struggling with a knee injury by digging deep to beat Camila Giorgi on Monday in a testing start to her Australian Open campaign.
In searing heat, the six-time Australian Open champion, who is gunning to equal Steffi Graf's Open-era record of 22 Grand Slam titles, ground down the Italian 6-4, 7-5 in 1hr 45 mins during her first round clash.
Wearing a canary yellow pleated skirt and matching mid-rift bearing shirt, displaying her pierced naval, Williams was composed but not her usual clinical self during the draining workout.
"It wasn't very easy, she plays really well," said the top seed, after successfully coming through her first tour-level match since the US Open in September.
"I haven't played a competitive match in a really long time so it was good for me to come out here and get through it.
"I was able to stay in it and stay calm and that is what matters most."
Leading into the match the lopsided statistics made the American an overwhelming favourite - she had won 737 tour matches and 69 singles titles to Giorgi's 248 and one.
And Giorgi's nerves were clearly jangling as she opened with a double fault with the heat hitting 32 Celsius on Rod Laver Arena.
But the world number 36 - the highest ranked non-seed - quickly settled down to hold serve with a scintillating crosscourt forehand.
With Williams' knee giving her problems in the latter half of 2015 and in the lead-up to Melbourne Park, the Italian did her best to push her around the court but the top seed was moving freely and held for 1-1.
Despite her lack of match practice, a focused Williams quickly got in her groove and carved out a decisive break with some powerful groundstrokes to grab a 2-1 advantage.
She held for 3-1 and broke again for 4-1 as the right-hander's confidence appeared to sap before the Italian regained composure to claw back to 4-2.
It was the start of a mid-set wobble by
Williams, who lost the next game and had to recover from 0-30 down on her serve
in the eighth to stay on top, screaming "Come on!" as she finally
went 5-3 clear. She served out the set in 43 minutes.
A 12-minute opening game in the second set, won by Giorgi, set the tone for a close match with Williams' rustiness starting to show as she failed to find the killer instinct.
It went to 5-5 before she finally got the break she was seeking, serving out to love to seal a hard-fought victory.
Williams dropped only three matches in 56 last season and won three majors, the Australian and French Opens and Wimbledon, before being deprived of a calendar-year Grand Slam at Flushing Meadows.
Those major titles took her to within one of Graf's long-time record of 22, and put her three clear of both Chris Evert and Martina Navratilova.
Melbourne Park has been a happy hunting ground. She claimed her first Australian Open title way back in 2003, beating elder sister Venus in the final, and reached her sixth last year when she toppled arch-rival Maria Sharapova.
Williams is in a tough half of the draw with Russia's Sharapova, seeded five, potentially awaiting her in the quarters.
Next up for the 34-year-old is either Taiwan's Hsieh Su-wei or Latvian Jelena Ostapenko.
Results from Australian Open Grand Slam at Melbourne Park on Monday:
Federico Delbonis (ARG) bt Ivo Karlovic (CRO x22) 7-6 (7/4), 6-4, 2-1 (retired)
Austin Krajicek (USA) bt Wu Di (CHN) 6-4, 6-1, 6-3
Kei Nishikori (JPN x7) bt Philipp Kohlschreiber (GER) 6-4, 6-3, 6-3
Mirza Basic (BIH) bt Robin Haase (NED) 7-6 (7/4), 6-4, 6-4
Daniel Brands (GER) bt Victor Estrella (DOM) 6-4, 7-6 (7/1), 4-6, 6-1
Dominic Thiem (AUT x19) bt Leonardo Mayer (ARG) 6-2, 7-6 (8/6), 4-6, 7-6 (7/0)
Damir Dzumhur (BIH) bt Kyle Edmund (GBR) 1-6, 7-6 (7/4), 4-6, 6-3, 6-1
David Goffin (BEL x15) bt Sergiy Stakhovsky (UKR) 3-6, 6-3, 6-4, 6-4
Serena Williams (USA x1) bt Camila Giorgi (ITA) 6-4, 7-5
Margarita Gasparyan (RUS) bt Sara Errani (ITA x17) 1-6, 7-5, 6-1
Magdalena Rybarikova (SVK) bt Yanina Wickmayer (BEL) 3-6, 6-3, 7-5
Anna-Lena Friedsam (GER) bt Lourdes Dominguez (ESP) 7-6 (7/3), 2-6, 6-1
Maria Sakkari (GRE) bt Wang Yafan (CHN) 6-4, 1-6, 6-3
Carla Suarez (ESP x10) bt Viktorija Golubic (SUI) 7-5, 6-4
Nicole Gibbs (USA) bt Klara Koukalova (CZE) 6-2, 2-6, 6-1
Daria Gavrilova (AUS) bat Lucie Hradecka (CZE) 7-6 (7/3), 6-4
Petra Kvitova (CZE x6) bt Luksika Kumkhum (THA) 6-3, 6-1