The service games of both players are looking fragile but Gauff fights her way into a position to set up the game with a forehand winner at deuce.
Kostyuk again looks to be aggressive but plays a sloppy backhand to allow Gauff to hold serve.
Kostyuk holds serve for first time in five games.
After a fast start to the match the Ukrainian had been giving up her serve too easily, but finally responds to make it 2-2 in the second set.
Kostyuk has something to build on as well, with a forehand winner followed by two Aces that clinch the game to 15.
Gauff breaks back then holds serve to take a 2-1 lead.
The second set is on track to be as unpredictable as the first, with Gauff breaking back immediately to 15 as Kostyuk again fails to hold her serve.
The unforced errors are building up on both sides but the American closes out her serve.
Kostyuk starts second set with a break.
The Ukrainian seems happy to show her emotions on the court but is just a quick to brush aside any disappointment.
After dropping the first set Kostyuk breaks Gauff to love.
Coco Gauff wins the first set against Marta Kostyuk 7-6 (8-6)
Gauff completes the comeback.
A rollercoaster first set carried on much the same way into the tie-breaker, but after trailing 1-5 and facing down several set points Gauff comes out on top.
Kostyuk had the first set within her grasp but three costly errors late in the tie-breaker hand it to the American at 8-6.
The first set tie-breaker remains in the balance with unforced errors on both sides making it 5-5.
Kostyuk rolls the dice with a forehand winner to clinch a set point at 6-5, but tries to end the next rally too quickly as another powerful forehand shot crashes into the net.
The tie-breaker is being decided off Kostyuk’s racquet, with a blistering backhand winner mixed among three errors that give Gauff a 4-2 lead.
A double fault from Gauff makes it 4-3 to the American, with the second serve not even close to clearing the net.
Here we go with the tie-breaker for the first set.
Kostyuk doesn’t even try to hide her emotions after starting the tie-breaker with a double fault, but bounces back immediately with a crosscourt backhand from the net to make it 1-1.
Kostyuk breaks back to take the first set to a tie-breaker.
The Ukrainian rediscovers her touch after losing five games in a row, and after dropping two break points from 15-40 wins the next two points to level the set at 6-6.
Kostyuk calls for a trainer to look at an issue with her left foot, and in particular the tape wrapped around it, as a medical time-out is called.
Meanwhile, Gauff heads back onto the court to keep her serve flowing – which played a significant part in her change of fortunes as the first set progressed.
Gauff breaks and leads the set for the first time.
A dramatic turnaround is almost complete on Rod Laver Arena as Gauff breaks Kostyuk to 15.
Gauff is the player now looking to hit winners while Kostyuk pays the price for another double fault with the game on the line at 15-40.
The American has won the last five games on the bounce and will now serve for the first set at 6-5.
Gauff holds serve to even up the set at 5-5.
The momentum has swung back to the American after Kostyuk raced out to a 5-1 lead in the first set.
Gauff’s first serve has warmed up and she has been able to then punish Kostyuk from the baseline or even win points at the net.
The No 4 seed closes out the game with an Ace and now has the Ukrainian on the ropes.
Gauff seals back-to-back breaks to tighten up the first set.
Kostyuk starts as she ended her previous service game – with a double fault.
Gauff follows up with a pair of winners – first on the forehand, then on the backhand – to again take a 0-40 lead off Kostyuk’s serve.
The Ukrainian fights back to 30-40 but an unforced error hands the game to Gauff and puts the set back on serve at 5-4.
Gauff holds serve after saving set point for Kostyuk.
The game goes to deuce as Kostyuk eyes the first set, but positive play from Gauff keeps the American alive at 5-3.
Kostyuk still has an opportunity to serve for the first set.
Gauff breaks back to stay in the set.
Another slow start to her service game from Kostyuk gives Gauff hope as the American edges in front at 15-30.
Kostyuk can’t turn it around this time as a pair of double faults allow Gauff to break back for the first time and makes it 5-2.
Kostyuk breaks Gauff for a second time.
The game goes to deuce and once again Gauff double faults to give Kostyuk an advantage then hits an unforced error to drop her serve.
The American’s first serve is failing her too often, going at 55%, and the Ukrainian is primed to pounce.
Kostyuk holds after trailing 0-40.
Gauff puts the pressure straight back on to Kostyuk, but in a confidence booster for the Ukrainian she fights back to deuce then closes out the game on the second attempt.
Kostyuk is picking her moments but seems to be more confident playing down the line, and has hit seven winners to Gauff’s one so far. It’s 4-1 to Kostyuk in the first set.
Kostyuk breaks Gauff.
In an early case of the live bloggers’ curse, the Ukrainian pushes out to a 30-0 lead until Gauff works her way back to 30-30.
A double fault hands the advantage back to Kostyuk as a costly error from Gauff on the next point makes it 3-1.
Kostyuk is again taken to deuce after first opening up a lead on her serve.
Some powerful hitting from the Ukrainian forces Gauff into a pair of errors that close out the game for a 2-1 scoreline, though the American looks threatening early.
The big-serving American Coco Gauff gets on the board, holding her serve to 30 without too much difficulty to make it 1-1.
Marta Kostyuk serves first against Coco Gauff as we get under way on Rod Laver Arena.
The Ukrainian controls the early points from the baseline to push out to a 40-15 lead, but some unforced errors allow Gauff back into the game.
Kostyuk looks frustrated as the early advantage slips away but after two break points for Gauff, the world No 37 holds serve to clinch an early 1-0 lead.
For a heart-warming tale on two decades of persistence paying off even on the tennis circuit, dive into Jack Snape’s interview with India’s Rohan Bopanna as he secures a career-high ranking – and potentially the men’s doubles No 1 – at the age of 43:
While we wait for the women’s singles quarter-final between Coco Gauff and Marta Kostyuk to start on Rod Laver Arena, a reminder of former world No 3 Elina Svitolina’s unfortunate exit from the tournament when facing Linda Noskova:
Conditions are perfect at Melbourne Park as quarter-final action kicks off at the Australian Open 2024 with the afternoon session on day 10.
The women’s singles will start with No 4 seed Coco Gauff facing Marta Kostyuk on Rod Laver Arena – you can follow that match here from 1pm local time.
Following that will be Novak Djokovic meeting Taylor Fritz, as the No 12 seed looks to upset the reigning champion. Joey Lynch will be on deck to keep you across that match.
We’ll also be covering the evening session including the heavyweight clash between the men’s No 4 and 5 seeds, Jannik Sinner and Andrey Rublev.
On the women’s side this evening, No 2 seed Aryna Sabalenka will be up against No 9 seed Barbora Krejcikova.
But for now, get in touch with any thoughts and ideas as we get into the business end of the tournament.