Day Four of the 2023 US Open is complete and with only a short time until Day Five begins, we take a look at what we learned from the latest action in Flushing Meadows.

Including John Isner's emotional farewell and Andy Murray soul searching after his early defeat to Dimitrov.

38-year-old John Isner was given a farewell in his first match with some in the USTA seemingly expecting that he wouldn't win his opener. But as ever with tennis, it is unpredictable and for Isner, he won through to a tie with Michael Mmoh.

He had the chance even to reach the third round, but Mmoh produced an almighty comeback which will be at the back of people's mind unless you dislike John Isner.

A player who helped anchor American Men's Tennis before Fritz and Tiafoe, he ended on a tiebreak in an ironic turn of events given that he was the first to reach 500 in the Open Era.

But it was a night of retirements as Jack Sock also bowed out from tennis alongside Coco Gauff in the mixed doubles. A player who led alongside Isner, but albeit eight years younger. He will go onto play pickleball, but the accolades are there for Isner.

Andy Murray is very much still able to play at a top level, but was left disheartened as he yet again couldn't produce at a Grand Slam as he hoped.

Losing out to Grigor Dimitrov who battled through an epic with Alex Molcan only two days prior, he even admitted post match that he was wondering if it was all worth it.

But that the only solace was that he continues to climb the rankings after being rock bottom previously.

Similar to Isner, it makes fans think whether he will continue if the passion and battle is not there and the wins in particular are not forthcoming.

He also said that he didn't deserve to play Davis Cup afterwards meaning a potential stint away on the sidelines could be forthcoming. But while Murray failed to deliver, Katie Boulter and Jack Draper who themselves have had injury battles (more than most) battled through for Brit hopes.

With Caroline Wozniacki and Jennifer Brady playing this evening after returning to the sport this summer, it is Elina Svitolina who gets all the accolades.

Rightfully so, with the Ukrainian in a boot two weeks ago and seemingly on course to end one of the best summers of her career injured and again having to come back.

But the boot came off and the form also came back. Caring more if her husband Gael Monfils had started his match on Grandstand during the tie, she dealt with Anastasia Pavlyuchenkova.

Next up is a real popcorn clash and one that will headline likely on Day Six against Jessica Pegula. One of America's finest hopes facing a player who the whole tour is super pleased to have back and playing some of her best.

While Wozniacki and Brady may have further success, it will be Svitolina who will likely take comeback player of the year at this early stage when the WTA Awards get released.

Similar to Novak Djokovic, Carlos Alcaraz who is his main rival to the title has been in truly sensational form.

The new sleeveless Alcaraz continued that in the New York heat by taking down Lloyd Harris successfully.

Albeit unlike his opener, there was no singing and he will hope to not be singing the blues and continue his unstoppable form when he faces Dan Evans.

Evans himself won recently in Washington so has been in title winning form and the 26th seed who has had a tumultuous road will hope to add to the Brit hopes and blaze his own trail by adding to a number of seeds who have headed home early.

But while in certain sections, it was a night to remember. It was firmly a night to forget for Matteo Berrettini.

Berrettini rolled his ankle seemingly in an injury that many thought was a lot worse. But he still left the court and the tournament in tears and in a wheelchair.

A player who like Svitolina many delighted in seeing return to some semblance of his best has been the recipient of some utterly torrid luck.

That continues and he will again likely have a stint off court that will be unwanted for the Italian as he fell to Arthur Rinderknech.