This one should be intriguing - Serena Williams v Simona Halep. Remember their encounter at Wimbledon in 2019? Perhaps the Romanian's finest-ever tactical display.

Another encounter with Naomi Osaka up next. Fascinating.

WILLIAMS 6-3, 6-3 HALEP: Serena takes a second match point - she's left Halep veritably stranded on the baseline at moments this evening. They greet each other with respect at the net. What a defensive performance from Williams.

WILLIAMS 6-3, 5-3 HALEP: A love hold for Serena Williams who's now one game away from yet another Grand Slam semi-final. This set has turned in her favour so quickly.

WILLIAMS 6-3, 4-3 HALEP: Halep hits her thigh with rage as she gifts a fourth break point to Williams, but the 10th seed can't capitalise. When it comes to the sixth break point, Halep benefits from the net twice, but can't finish off the rally. A break for Serena.

WILLIAMS 6-3, 3-3 HALEP: That first serve is still not looking particularly good from Williams, but she clings on to hold.

WILLIAMS 6-3, 2-3 HALEP: Four breaks of serve in a row! Cahill now looks slightly concerned. This is a see-saw set. We're moving into a second hour on court.

WILLIAMS 6-3, 1-3 HALEP: Darren Cahill is on his feet applauding Simona Halep, who's still snaffling those errors on the Williams serve.

WILLIAMS 6-3, 1-2 HALEP: Good recovery from Williams here to break back, pushing Halep wide. Back on serve.

WILLIAMS 6-3, 0-2 HALEP: A very poor game from Williams, with her first serve falling apart and gifting the points to a happy Halep.

WILLIAMS 6-3, 0-1 HALEP: This is an epic, seven minutes of duelling, but in the end Serena's unforced errors help out her opponent. The hitting isn't quite as crisp as in the first set, but still some excellent shot-making, a lovely cross-court blitz that brushes the line from the American.

WILLIAMS 6-3 HALEP: Halep breaks a string in the first rally of the game, and plays two more shots before having to switch rackets. And Serena Williams serves out to love to take the first set, with a look of utter focus on her face.

WILLIAMS 5-3 HALEP: A hold to love for Simona Halep, the first one for either player so far today. Serena will try to serve the first set out.

WILLIAMS 5-2 HALEP: Backing up the break with a strong hold, and Serena moves to within a game of the opening set. Just over half an hour gone here.

WILLIAMS 4-2 HALEP: Simona Halep is not happy about game point, which looks like it landed on the line, but without a challenge system and with automated line calling, she has no recourse. Delightful battle.

WILLIAMS 3-2 HALEP: Serena is hitting well on both flanks, with Halep trying to get her moving into the corners.

WILLIAMS 2-2 HALEP: Halep coming back with aggression wrongfoots Williams slightly, who can't quite make her decisions quickly enough.

WILLIAMS 2-1 HALEP: Lovely from Halep. She's playing very well, by the way, adopting the same tactics as she did in that Wimbledon final, but Williams is also playing much better than she did that day.

WILLIAMS 2-0 HALEP: Serena's extension is simply brilliant. She's fending off the Halep attack and although she gets some help from the net, this is powerful.

WILLIAMS 1-0 HALEP: The Serena serve on song as she gets under way here, finishing the game with an ace.

Importantly, the player who's won the first set has gone on to win the entire match in ten of their previous 11 meetings.