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
Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
Does Youzhny believe he can do anything? How he started the match was going to be key and it went by the wayside for him quickly. It is probably a pretty lonely place for him down there.
Federer 6-1 Youzhny*
That was dismissive from Federer. The set lasted just 26 minutes and he's hit 13 winners to Youzhny's five, with just seven unforced errors to the Russian's 13.
David Law
Radio 5 live sports extra commentator at Flushing Meadows
That is about as comfortable a first set as Roger Federer will have ever played in his life.
Image source, AFPFederer 6-1 Youzhny
Mikhail Youzhny's record against Federer isn't going to get better any time soon.
He has three set points on his own serve, and he needs just one to take the first set.
Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
Rublev is a star of the future. He is making serious waves. He has got confidence, pace, power and is relentless in his approach.
These young guys playing without any fear. They are so dangerous right now.
Dimitrov 5-7 6-7 (3-7) 3-6 Rublev
All over.
It is the biggest win of 19-year-old Andrey Rublev's career. He has knocked out seventh seed Grigor Dimitrov.
And what a way to seal it. The Russian slaps a forehand onto the sideline for a winner.
*Federer 5-1 Youzhny
There's a very warm round of applause for Mikhail Youzhny as he gets himself on the board in this first set. He's only really delayed the inevitable, but it's a hold nonetheless.
*Federer 5-0 Youzhny
The third game point for Youzhny now, and again he's beaten by a Federer drop shot. Three times in one game he's played that shot.
Youzhny sends his serve out wide and a sprawling Federer nets his return but, perhaps understandably, Youzhny is all out of kilter. He comes forward, looking to smash a winner, and nets.
His head drops and its dropping even more as Federer forces him to go long with the forehand. That brings up second point, but Federer sends a nothing sort of forehand into the net.
*Federer 5-0 Youzhny
An ace from Youzhny brings up the advantage, but he goes down the line with the backhand and there's too much on it. Deuce number two.
This time Youzhny gets the best of some net play with a backhand volley, but the attempted winner is ill-directed again and the ball sails harmlessly over the baseline.
Federer has time to line up his shots and he takes advantage, pushing Youzhny wide, and the Russian's backhand finds the net. Here's set point - and there it goes! Federer nets the backhand.
David Law
Radio 5 live sports extra commentator at Flushing Meadows
This is exhibition stuff from Federer.
Image source, Reuters*Federer 5-0 Youzhny
Mikhail Youzhny is racing to a love hold and then Federer unfurls a beautiful backhand drop shot, carving the ball over the net and Youzhny can't get near it.
And now he forces Youzhny to come running forward before whipping a forehand winner into the exact spot the Russian was stood in a moment before.
Oh, that is obscenely good from Federer. Another backhand winner, delicately floated over the net, and Federer has forced deuce.
Federer 5-0 Youzhny*
We've been going for 15 minutes. That's a quarter of a Game of Thrones episode.
Federer 5-0 Youzhny*
There's an almighty click of cameras as Federer pauses, throws the ball into the air and serves.
That's a beautiful bit of work, picking up a return from right on the baseline before shimmying forward to meet Youzhny's forehand and belt a winner.
Fed then consolidates this ridonkulous start by pushing Youzhny out wide with the serve and then sending the return the opposite way. He's a game away from taking the opening set.
Image source, ReutersLeon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
We get so excited about Dimitrov, thinking now he is really going to challenge, but all of a sudden, whether it is an off-court problem, something knocks him off.
Image source, EPADimitrov 5-7 6-7 3-5 Rublev
It's all going horribly wrong for Grigor Dimitrov.
Russian teenager Andrey Rublev has raced into a 5-2 lead in the third set and is now just a game away from knocking out the seventh seed.
*Federer 4-0 Youzhny
The first advantage goes Youzhny's way, but he nets, before a lacklustre forehand finds the net.
Federer, not missing a beat, cracks a forehand winner with ease to go a double break up.
*Federer 3-0 Youzhny
I wonder if I'll ever be as good at anything as Federer is at tennis. I suspect not.
Not that he's been tested much in these opening stages. Youzhny gets to 40-30 as Federer nets two backhands but there's not a lot of pace coming from the Russian's racquet, and his forehand drifts wide for deuce.
Federer 3-0 Youzhny*
Fed, headband firmly in place, feeds Youzhny's backhand but the Russian hasn't got the pace of this court, and he nets.
That's 40-0, and a long forehand from Youzhny hands Federer the game.
#bbctennis
John McEnerney: Fed might not find his range right away like in round one but he'll have too much for Mikhail Youzhny in New York but it could go four sets.
*Federer 2-0 Youzhny
A forehand winner from Federer is followed up by a double fault from Youzhny, and his serve sits up nicely for Federer to whack in a forehand, and Youzhny nets his return.
Three break points come whizzing along, and the Russian saves the first with a little dink over the net.
Youzhny coughs up another double fault! An early, gifted break for Federer.