Federer beats Youzhny 6-1 6-7 (3-7) 4-6 6-4 6-2
Rogers and Gavrilova play longest women's match in US Open history
World number one Pliskova beats Gibbs 2-6 6-3 6-4
Seeds Dimitrov and Berdych knocked out, Del Potro through
Day four of US Open at Flushing Meadows
Simon Cambers
Tennis journalist at Flushing Meadows
The way this tournament is going, someone like Berdych might have thought he had a chance here. But he's not had a great year and that's a bad result for him.
Dolgopolov 3-6 6-1 7-6 (7-5) 6-2 Berdych
Another seed falls at Flushing Meadows!
This time it's Tomas Berdych, who has been dispatched in four sets by Ukraine's Alexandr Dolgopolov.
The 15th seed made 57 unforced errors compared to Dolgopolov's 29, and had 12 double faults to his opponent's four.
Image source, Reuters*Ka Pliskova 2-6 2-2 Gibbs
Brilliant play from Gibbs. World number one Pliskova fights to 30-30 so you could forgive 127-ranked Gibbs for getting a little tight but there are no signs of that.
Two winners, one off the forehand and one off the backhand, seal the game.
20 winners now for Gibbs, three more than Pliskova. Can she keep this up?
Rublev 7-5 Dimitrov
Three set points came and went for Andrey Rublev, but he's snaffled the first set at the fourth time of asking!
Image source, AFPKa Pliskova 2-6 2-1 Gibbs*
The sun has dipped behind some very dark clouds above Flushing Meadows. That should help the server I suppose.
Pliskova has been very inconsistent in this match and her groundstrokes just don't seem to be going through the court.
Just as I say that she hits a backhand winner to edge in front in this set.
Piers Newbery
BBC Sport at Flushing Meadows
"Is that Andy Murray's younger brother?"
Well, you're nearly right sir. The presence of big brother Jamie and Bruno Soares has got them packed in around court six, the crowd noise vying with the din coming from the adjacent Sports Cafe. Judy Murray is seated in the main stand as her eldest and his Brazilian partner recover an early deficit against Julian Knowle and Alexander Peya.
*Ka Pliskova 2-6 1-1 Gibbs
Another clench of the fist from Gibbs as she battles through a difficult game to level in this second set. Her serve is much slower than her opponents but excellent accuracy is keeping her just a couple behind in the aces count.
Ashe is starting to fill up a little. The locals have realised one of their own could cause a big upset.
Image source, AFP*Rublev 6-5 Dimitrov
Hmm. Dimitrov's backhand has just lost a bit of oomph as he slices a return into the net, before Rublev has the Bulgarian doing the splits as he stretches to meet a forehand.
Dimitrov furiously swipes his racquet in the air as the Russian holds to love, before his serve saves a break point as Rublev lashes his return wide.
Another break point comes up - and Dimitrov double faults! A serve out wide is pushed too far, before the second serve finds the foot of the net. Rublev will serve for the first set.
Piers Newbery
BBC Sport at Flushing Meadows
What better way to start a day of elite-level sport (watching) than with some very necessary refuelling. That is one area in which the US Open excels, with five restaurants and 60 concession stands knocking out a variety of calorie-busting grub. It's hard to beat a good old hotdog though (this is not me).
Just one of the 225,000 hamburgers and hot dogs that will be demolished during the tournament, food fact fans.
Image source, BBC SportSimon Cambers
Tennis journalist at Flushing Meadows
The way things have gone in the past few months, Garbine Muguruza is the best player in the world at the moment. No-one would be surprised if she got to number one, and she deserves it.
Ka Pliskova 2-6 1-0 Gibbs*
Pliskova could be forgiven for breathing a big sigh of relief. Her famous serve comes to the rescue to see her through this first game of the second set.
Nicole Gibbs is in a very colourful neon outfit. Pink shoes, a blue top with multi-coloured stripes and a neon cap. Her play so far has matched it. She has been a bundle of energy.
*Ka Pliskova 2-6 0-0 Gibbs
Big danger for world number one Pliskova now.
A break point right at the start of this second set.
Saved with an ace. Deuce...
*Rublev 4-5 Dimitrov
Rublev had break point at 30-40 but Dimitrov's serve got him out of a stodgy situation, before a long rally went the Russian's way as a Dimitrov backhand floated wide.
There's a brief tussle between the two, points going this way and that - but Rublev draws the error out of Dimitrov's forehand to get the match back on serve!
Osaka 6-3 4-6 7-5 Allertova
Naomi Osaka, conqueror of Angelique Kerber in the first round, has continued her good form.
The 19-year-old has reached the third round with a nicely-paced victory over the Czech world number 90. She's never reached the second week of a Slam before...
Image source, AFP/Getty Images
Russell Fuller
BBC tennis correspondent at Flushing Meadows
Nicole Gibbs had three unforced errors and 14 winners, compared to eight winners and 15 unforced errors from Pliskova. That does tell the story. The serve isn't as good as usual and she looks lethargic. It's not the Karolina Pliskova we're used to seeing.
Image source, ReutersKa Pliskova 2-6 Gibbs
A 15th error of the set comes off the Pliskova racquet and the world number one loses the first set.
Nicole Gibbs clenches her fist. Her home crowd cheer on Arthur Ashe. A brilliant start for her. Is an upset of on the cards?
It is no surprise to see Pliskova head off the court at the end of the set to try and refresh.
Image source, ReutersKa Pliskova 2-5 Gibbs*
Outstanding contribution that from Gigi.
Just as with the lack of carp, Pliskova won't be a big fan of how she has started this match as she falls 30-0 behind in a game the world number one has to win to stay in the set.
A backhand winner for Pliskova follows but that can't stop the American charge.
Nicole Gibbs brings up two set points...
Gigi Salmon
BBC Radio 5 live sports extra commentator at Flushing Meadows
Pliskova, in her free time, is a big fan of carp fishing. She said she doesn't get an awful lot of time to fish for carp because of her tennis schedule and not all the places she travels are conducive to it.
Russell Fuller
BBC tennis correspondent at Flushing Meadows
Pliskova is serving better in this game but she's lacking in confidence. There was no conviction behind some of those shots. Odd.
Ka Pliskova 2-5 Gibbs*
Pliskova stops the run of five consecutive games against her by holding serve but even that wasn't simple.
She misses a regulation volley which takes us to deuce but eventually sees the game out at the second attempt.
Both players head to their seats. The spring is clearly in the American's step. She'll serve for the set in a couple of minutes.