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
*Federer 6-1 6-7 (3-7) 4-6 1-1 Youzhny
Tense faces aplenty around Arthur Ashe as the clocks tick into the second hour.
Federer celebrates by cracking down his 47th and 48th unforced errors. A 98mph serve from Youzhny, and Federer just floated it into the net.
Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
You have to take your hat off to how Youzhny has served that set out. There should have been a bundle of nerves. The first point was key. If Roger had made him play it could have been different.
What an opportunity for Youzhny. All eyes are on Roger. How will he react to this now?
Federer 6-1 6-7 (3-7) 4-6 1-0 Youzhny*
A hold from Federer, consolidated with a sharp backhand volley at the net. That's the first shot in some while that's had a touch of elegance about it.
*Federer 6-1 6-7 (3-7) 4-6 Youzhny
In that last set, Federer had 17 unforced errors to Youzhny's six.
He'll serve to begin the fourth set.
Image source, AFP
David Law
Radio 5 live sports extra commentator at Flushing Meadows
Suddenly Mikhail Youzhny has developed Stan Wawrinka's backhand and Juan Martin del Potro's forehand.
I have never seen him play this well.
*Federer 6-1 6-7 (3-7) 4-6 Youzhny
Get your upset klaxons at the ready.
Roger Federer trails the man you could reasonably have called his bunny by two sets to one.
Image source, Reuters*Federer 6-1 6-7 (3-7) 4-5 Youzhny
A stonking forehand from Youzhny flummoxes Federer, who swats at the ball and gets a top edge that flies wide.
And three set points come up as Federer charges past a forehand winner...
Federer 6-1 6-7 (3-7) 4-5 Youzhny*
Here we go. Mikhail Youzhny, serving to take a two-set lead against the man who has beaten him 16 times.
Piers Newbery
BBC Sport at Flushing Meadows
The drama is not just confined to Ashe - American Shelby Rogers drops to her knees in tears on Court 19 after winning the longest women's match in US Open history. Rivers beats Australian Daria Gavrilova 7-6 4-6 7-6 in a lung-busting three hours and 33 minutes. Next up for Rogers, fourth seed Elina Svitolina.
Federer 6-1 6-7 (3-7) 4-5 Youzhny*
Done, at the third time of asking. Youzhny will have to serve out this third set.
Image source, Getty ImagesFederer 6-1 6-7 (3-7) 3-5 Youzhny*
Federer gets the advantage for the first time but he knows he's fluffed from the moment the ball leaves the racquet as his forehand flies long.
Can he clinch this game at the second time of asking? No! A superb backhand from Youzhny, all flight and guile, lands smack on the baseline. Deuce, my old friend, we meet again.
Federer 6-1 6-7 (3-7) 3-5 Youzhny*
Saved yet again by the Swiss, who pushes Youzhny out wide and the return is shanked long.
Federer 6-1 6-7 (3-7) 3-5 Youzhny*
That's pants from Federer. A simple backhand volley doesn't get more than a foot off the ground.
Set point number two for Mikhail Youzhny...
Federer 6-1 6-7 (3-7) 3-5 Youzhny*
Saved with a forehand smash. 40-40.
Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
That was a very poor miss from Roger Federer. He had the open court. That just shows how rattled he is.
Image source, Rex FeaturesFederer 6-1 6-7 (3-7) 3-5 Youzhny*
Mikhail Youzhny! That is an extraordinary stroke down the line, a perfectly floated forehand that Federer can't, and won't, get near.
Federer claws it back to 30-30, he has an acre of blue space for his backhand volley - and he fluffs it! He's too open stanced and that's handed Youzhny set point...
*Federer 6-1 6-7 (3-7) 3-5 Youzhny
Roger may be struggling but the ball is flying of Youzhny's strings. He starts the game with a thumping forehand winner.
Federer gets a winner of his own with a much needed clean strike on the backhand. A volley spins and drops dead on the court from the Swiss. 30-30.
But now two balls hit long from Federer. That just wasn't happening in the first set. He's in big trouble.
Federer 6-1 6-7 (3-7) 3-4 Youzhny*
Fed's face is inscrutable as he whizzes through a love hold.
Leon Smith
Great Britain Davis Cup captain on BBC Radio 5 live sports extra at Flushing Meadows
The ball speed has dipped especially on Federer's backhand side when Youzhny gets the ball higher. It is just error after error right now.
*Federer 6-1 6-7 (3-7) 2-4 Youzhny
Youzhny makes full use of the speed from the new balls as a backhand befuddles Federer. His coaching team have got their feet tapping nervously.
That backhand from Youzhny, though. It's lovely, coming back at Federer at a nice pace and height, and the Russian holds to extend his lead.
Image source, AFP