PERTH (AUSTRALIA) - If the Hopman Cup is anything to go by, world number one Serena Williams has some serious fine-tuning to do if she wants to claim her 19th Grand Slam title at the Australian Open later this month.
Serena Williams of the US hits a return against Agnieszka Radwanska of Poland during their women's singles final match on day seven of the Hopman Cup tennis tournament, in Perth, on January 10, 2015
The 33-year-old spluttered her way through the mixed-team tournament in Perth, with moments of brilliance interspersed with extended periods of erratic play.
Her moods matched her form and it culminated in a listless performance in the final, as she and fellow American John Isner were upset by Poland's Agnieszka Radwanska and Jerzy Janowicz.
A clearly frustrated Williams was beaten by Radwanska for the first time in nine outings, and the American also struggled, particularly on her serve, in the deciding mixed doubles.
The sometimes feisty Williams also lost her cool after a contentious point during the doubles, appearing to call the chair umpire a "liar" as the tournament referee was called to the court to resolve the disagreement.
Minutes later she smashed a racquet in frustration after missing a volley at the net.
Williams, who was denied a record third Hopman Cup title, claimed she was suffering from fatigue early in the tournament and said she could play "two thousand times better".
Her singles form was mixed, opening the tournament with a come-from-behind win over Flavia Pennetta after failing to win a game in the first set.
It was during that match that Williams bizarrely called for a shot of coffee when trailing 5-0 in the first set.
She was then thrashed by world number six Eugenie Bouchard, 6-2, 6-1, before edging past the Czech Republic's Lucie Safarova in three sets.
Speaking after her win over Safarova, Williams conceded she was down on form heading towards the year's first Grand Slam.
"I have been practising so well, I just have not been able to put it through in my matches," she said.
"Hopefully it will be able to come through soon.
"I do I feel like I am getting back into the groove, I am not moving as well as I was last year.
"I am going to try and improve that and I know I can so but I am getting there."
Williams said the heat in Perth was beneficial for her Australian Open preparations.
Williams is the defending US Open Champion, but has not won the Australian Open since beating Belgium's Justine Henin in the 2010 final.
She was beaten by Serbian Ana Ivanovic in the fourth round last year in Melbourne.