Melbourne - Serena Williams has the Open-era record for Grand Slam titles within her grasp but it's getting tougher at the top as the American great seeks finally to eclipse Germany's Steffi Graf.
Victory at this month's Australian Open and a 23rd major win would help ease the heartache of last year, when Williams slipped off the top of the rankings after 186 weeks - matching, but just failing to beat, another Graf record.
Williams' drop to world No 2 was triggered by her shock defeat to Karolina Pliskova in the US Open semi-finals, which also denied her another chance to better Graf's 22 Grand Slam victories.
Pliskova was the sixth player to beat Williams in 2016, suggesting that the women's tour is becoming increasingly challenging for the 35-year-old.
Last year, Williams' haul of two trophies was her smallest since her injury-hit 2011.
It also took her four attempts move off 21 Slam titles and equal Steffi Graf's record of 22 - slow by her standards, after she won three out of four majors in 2015.
"It gets harder the older you get and the young ones coming up," said US Fed Cup captain Mary Joe Fernandez, after Williams' defeat to Pliskova.
"I think she is going to win more and break Steffi's record. But it's going to get tougher."
Williams is already the oldest player in the top 10 and she is 19 years senior to Australia's Destanee Aiava, who next week will become the first player born this century to play in a Grand Slam.
'HIGHEST OF GOALS'
Williams is no slouch at the season's opening Grand Slam, which she has won six times, although only once in the last six editions.
If she lifts the trophy on January 28, she will be one step away from Margaret Court's all-time record of 24 Grand Slam titles. No other active player has more than the seven won by Williams' elder sister, Venus.
Williams has only played two matches since her US Open defeat in September after she skipped the end of last season to recover from injury.
She made a scrappy return to action this month, sending down, by one count, 88 unforced errors in a wind-affected second-round defeat to compatriot Madison Brengle, the world No 69.
"I'm trying to think of a word that's not obscene but that's pretty much how I played," Williams fumed.
But Williams starts the season buoyed by her recent engagement to Reddit co-founder Alexis Ohanian, and her coach Patrick Mouratoglou is hoping the relationship will pay dividends on the court.
"I think players need stability because everything is changing every day: countries, surface, opponents, conditions, everything," he told The New York Times.
"And if she's happy, there's no reason why it wouldn't positively affect her tennis."
And there seems little doubt that Williams' single-mindedness will ultimately yield that elusive 23rd major win, even if it doesn't happen this month in Melbourne.
"Unfortunately I have the highest of goals and obviously that involves winning Grand Slams and that's all," she said in Auckland.