Neither player has come close to losing their serve so far. Williams takes us to 2-1 with a hold to 15 after Sakkari sent a forehand too long.

• Jennifer Brady (US, 28) v Yulia Putintseva (Kaz, 23)
• Naomi Osaka (Jpn, 4) v Shelby Rogers (US)

Still to be decided

• Alize Cornet (Fra) or Tsvetana Pironkova (Bul) v Maria Sakkari (Gre, 15) or Serena Williams (US, 3)
• Victoria Azarenka (Blr) or Karolina Muchova (Cze, 20) v Elise Mertens (Bel, 16) or Sofia Kenin (US, 2)

Always good to start off your first service game with an ace, even better starting off with two aces - taking Sakkari's total to 19 throughout the tournament.

Her third ace comes seconds later and that is a hold to love. A statement of intent from the Greek player, aiming to be the first from her country to advance into a Grand Slam quarter-final.

An early hold from Serena. She is playing in the last 16 of a Grand Slam for an incredible 62nd time and is aiming to move into the quarter-finals of a major for a 53rd time.

This is also her 19th time in the last 16 of the US Open, and she has only fallen at this hurdle twice.

Half the court is in the light, with the other half covered in shadow.

Williams starts off with a double fault, but soon belts an ace down the middle.

Serena Williams, who is aiming for her seventh US Open title, gets us going in this last-16 tie as she serves first.

On Arthur Ashe Stadium we have a last-16 tie between third seed Serena Williams and Maria Sakkari of Greece, the 15th seed.

These two met a couple of weeks ago in the last 16 of the Western and Southern Open, which Sakkari taking the win, 5-7 7-6 6-1.

BBC Radio 5 Live Sports Extra

We have live commentary of this evening's action on BBC Radio 5 Live Sports Extra so press play at the top of this page to listen along.

Britain's Laura Robson wants a drama-free day today...

Russell Fuller
BBC tennis correspondent

Novak Djokovic must have known his US Open was over as soon as that tennis ball hit a line judge in the throat.

Tim Henman had to be disqualified when he accidentally hit a ball girl on the ear in a men's doubles at Wimbledon in 1995; and so, too, did David Nalbandian when he kicked an advertising hoarding into a line judge's shin in the Queen's Club final of 2012.

The rules are clear and they must equally apply to the world's number one male player.

Djokovic spent seven minutes trying to persuade US Open referee Soeren Friemel of the case for the defence. But having hit a ball "dangerously or recklessly within the court, or with negligent disregard of the consequences" - to quote the rulebook - there were no grounds for clemency.

Read more of Russell's article here.

Djokovic quickly left the stadium without holding a news conference after his disqualification, but then posted a lengthy apology on Instagram.

He wrote: "This whole situation has left me really sad and empty. I checked on the lines person and the tournament told me that thank God she is feeling ok. I‘m extremely sorry to have caused her such stress. So unintended. So wrong.

"I’m not disclosing her name to respect her privacy. As for the disqualification, I need to go back within and work on my disappointment and turn this all into a lesson for my growth and evolution as a player and human being. I apologize to the @usopen , externaltournament and everyone associated for my behavior.

"I’m very grateful to my team and family for being my rock support, and my fans for always being there with me. Thank you and I’m so sorry."

Top seed Novak Djokovic was disqualified from the US Open on Sunday for accidentally hitting a ball at a line judge in his fourth-round match.

Djokovic, 33, showed his frustration after losing serve to trail 6-5 against Spain's Pablo Carreno Busta.

The Serbian world number one took a ball out of his pocket and hit it behind him, striking the female line judge in her throat.

After a lengthy discussion, he was defaulted by tournament officials.

A United States Tennis Association statement said: "In accordance with the Grand Slam rulebook, following his actions of intentionally hitting a ball dangerously or recklessly within the court or hitting a ball with negligent disregard of the consequences, the tournament referee defaulted Novak Djokovic from the 2020 US Open.

"Because he was defaulted, Djokovic will lose all ranking points earned at the US Open and will be fined the prize money won at the tournament in addition to any or all fines levied with respect to the offending incident."

Hello and welcome along to BBC Sport's coverage of day eight of the US Open.

Whatever happens today, it probably won't be as dramatic as what we saw yesterday...

Image source, Getty Images

Serena Williams is aiming to match the record of most Grand Slam titles won as she needs one to equal Margaret Court's 24.

Serena has safely negotiated week one of the US Open and it's last-16 action for her today.