Kei Nishikori joined the list of top seeds to bow out of the 2019 US Open while Roger Federer, Serena Williams and Novak Djokovic sailed smoothly into the fourth round at Flushing Meadows on Friday.

With plenty of big names – like Dominic Thiem, Stefanos Tsitsipas, Sloane Stephens, Petra Kvitova and Angelique Kerber – being knocked out in the first couple of rounds, Friday was expected to throw up some more surprises. And it did, with Nishikori losing in four sets and Grigor Dimitrov winning in three.

But the genuine title contenders all booked their places in the round of 16 with the likes of Federer, Serena and Djokovic notching up emphatic victories.

Here’s a look at the five biggest talking points from Friday’s US Open action:

Djokovic sets up showdown with Wawrinka

The rest of the field must’ve licked their lips after Djokovic got treatment done on his left shoulder in the second round. The defending champion, who has been in a league of his own since winning Wimbledon last year, was anxious about his shoulder heading into his third round match against Denis Kudla. But he put all doubts to rest with yet another dominating performance. The 32-year-old won 6-3, 6-4, 6-2 and informed after the match that he was pain-free.

He’ll have his task cut-out in the next round, though, as he’ll be up against Stanislas Wawrinka, a man who knows how to turn it on at the biggest stage. The Swiss is in decent form at the moment, having dropped just two sets in his three wins so far. On Friday, he defeated unseeded Paolo Lorenzi in straight sets and will now be keen to get the better of Djokovic once again. Although the Serb leads their head-to-head 19-5, Wawrinka has won the two biggest matches they’ve played against each other – the finals of the 2015 French Open and the 2016 US Open. This is surely one of the most highly-anticipated clashes of the pre-quarters in the men’s draw.

2014 finalist Nishikori stunned by De Minaur

The Japanese seventh seed was by no means expected to go all the way but his rather straightforward defeat to Australia’s Alex de Minaur did come as a surprise. Nishikori, the 2014 US Open finalist, came into the tournament after losing in straight sets in the second round of Cincinnati to unheralded compatriot Yoshihito Nishioka. And his poor form continued as he was beaten 2-6, 4-6, 6-2, 3-6 by De Minaur.

The highly-rated Australian will now face Dimitrov, who got a walkover against 12th seed Borna Coric in the second round before beating Kamil Majchrzak in straight sets on Friday. This is De Minaur’s best ever performance at a Major and given Dimitrov’s poor run of form, there’s a good chance he could go even further this year in New York.

Federer, Serena back to best

Ahead of the tournament, Federer had said that he hadn’t felt this good coming in to the US Open in a long time. But his recent results on the court said otherwise. After a bitter loss to Djokovic in the Wimbledon final, the 20-time Grand Slam champion suffered a shocking first round defeat to Andrey Rublev at Cincinnati. To add further doubts to his claim on a title he last won in 2008, Federer dropped the opening sets of his first two matches.

However, normal service resumed as the Swiss was back to his imperious best in a 6-2, 6-2, 6-1 masterclass against Daniel Evans. He next faces 15th seed David Goffin in the forth round, the stage where he was stunned by John Millman last year.

Another great of the game who hit top gear on Friday was Serena. The 23-time Major winner, who suffered a bit of a hiccup as she lost the first set in her previous match against 17-year-old Caty McNally, didn’t waste much time in dispatching Karolina Muchova 6-3, 6-2 in the third round. The 37-year-old will face 22nd seed Petra Martic next and a 24th Grand Slam title, tying her at the top of the all-time list with Margaret Court, seems a real possibility.

Medvedev meltdown

Arguably the most in-form player in the men’s field heading into the tournament was Daniil Medvedev. The Russian has reached three consecutive finals – Washington Open, Rogers Cup and Cincinnati – in three weeks before the US Open and is regarded as one of the gen-next players who can break the big three’s hegemony at the top.

Despite the workload, the fifth seed hasn’t really lost form in the tournament so far, dropping just two sets in his first three victories. But he did have a bit of an incident during his hard-fought 7-6, 4-6, 7-6, 6-4 win over veteran Feliciano Lopez on Friday.

The 23-year-old raised his middle finger to the crowd and thanked them after the match for booing him and thus motivating him. He later regretted his actions and vowed to give a better account of himself the next time but one hopes such incidents don’t get the better of him going forward. It’ll be a shame if his mental fragility leads to a loss when his game seems to be peaking.

Svitolina, Keys on collision course

One of the most exciting round of 16 clashes in the women’s draw has to be fifth seed Elina Svitolina’s match against 10th seed Madison Keys. Svitolina is in the fourth round of the US Open for the third straight year, with this being the furthest she’s ever gone in the tournament. The Ukrainian suffered back-to-back defeats to Sofia Kenin at the Rogers Cup and Cincinnati Open but is yet to drop a set so far in New York.

Keys, who reached the final here in 2017, hasn’t dropped a set in her first three victories either. The American is in top form at the moment, having bagged the title at Cincinnati, and will be spurred on by the home support when she takes on Svitolina on Sunday. This promises to be a cracking encounter as both players hit hard from the baseline and are high on confidence. Despite being lower ranked, Keys has to be given a slight edge.