The build-up to the US Open and the final major of the 2018 season begins on Monday for some of the leading players on the WTA Tour at the Mubadala Silicon Valley Classic.
The tournament is being held in San Jose, California for the first time, with the event previously being held in Stanford.
Here is a look at some of the leading players to watch out for during the week's action, with the final taking place on August 5.
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The 23-time major winner underlined she is back and a serious contender again with her run to the final at Wimbledon, where she fell short to Angelique Kerber.
The challenge now for Williams, who is back up to No 27 in the WTA rankings, is to show she has the consistency and stamina to re-establish herself at the top of the women's game.
The American's game is still a work in progress as she finds her range after 14 months out of the game to become a mother. The power is still there, as she demonstrated at Wimbledon, but her movement at the back of the court was still a little off, and was capitalised on by Kerber. That will be something she will look to work on in California.
Williams, seeded No 6, has Johanna Konta in the first round. Twelve months ago this would have been a tough call, but the Briton has had a poor 2018 and has only won five games against players in the top 32 this year so far.
Williams, 36, won the event when it was in Stanford three times, most recently in 2014. She will fancy her chances of a strong run and a first tournament title since the 2017 Australian Open.
The top seed and world No 7 will be keen to bounce back after her Wimbledon title defence ended in the second round earlier in July with a shock defeat to Alison Van Uytvanck.
The two-time major winner has flattered to deceive this year. Her lone title in 2018 came in Monterrey in April, but two final appearances and two semi-finals is not reflective of her talent.
The 24-year-old Spaniard has a bye to the second round where Victoria Azarenka is a possible opponent. With the draw as it stands, Muguruza should expect to go deep in the tournament and hope to win her first title on American shores since Cincinnati last August.
The American will hope that history can repeat itself as she seeks to defend the title she won 12 months ago in Stanford.
Keys, 23, impressed when she beat Muguruza in the semi-finals before beating fellow American Coco Vandeweghe in the final.
She used that momentum to reach her first grand slam final at the US Open where she lost to compatriot Sloane Stephens.
Keys has had a solid, if unspectacular, season so far, the highlight being a semi-final run at the French Open where she again lost to Stephens.
As No 2 seed Keys will be confident of reaching the final in San Jose, although being in the same half of the draw as Serena Williams could set up a potentially tricky semi-final showdown.
The American is in the other half of the draw to her younger sibling Serena and so they can only meet in the final if both find their form.
Williams, 38, remains one of the top names in the women's game, and as world No 14 she enters the San Jose event as the third seed.
After winding back the years in 2017 with runs to the Australian Open and Wimbledon finals, the seven-time major winner has struggled to make as much of an impact this year: a semi-final at Indian Wells is her best effort of 2018 so far.
Williams will meet either Heather Watson or Claire Liu in the second round, with Muguruza a possible semi-final opponent if she makes it to the weekend.