Jeff Tarango
Former professional tennis player on 5 live sports extra

Wawrinka, by the way, is yet to beat Federer on hard courts - he's 0 for 8, as the Americans say. This is a must-win set for the fourth seed.

A double-fault and a typically picturesque leaping forehand from Federer take him to 30-30, and he opens up the court masterfully to give himself a forehand down the line for break point.

Terrific response from Stan, bludgeoning an inside-out forehand into the corner. Two big serves complete the escape act, and that's a big hold.

John McEnerney:  Fed looking majestic but Stan is no slouch this hopefully will go the distance after that walkover by Novak. Federer in four.

Sara Orchard
BBC Radio 5 live sports extra commentator

Now look, I'm a modern man, in touch with my feminine side and all that, but I'm not sure I'd be too comfortable wearing the Federer get up down the local municipal courts. White polo with pink collar and piping, shorts with pink piping, pink wristbands and pink trainers. It's...zingy.

Still, it's not doing Federer any harm out there - a slightly too aggressive Wawrinka sends some potent groundstrokes over the baseline and into the net to bring up two set points. Another forehand flies long from Stan, and that's the set.

Jeff Tarango
Former professional tennis player on 5 live sports extra

One thing Federer has been brilliant at over the years is sending the ball about a gnat's width over the net with the velocity of a speeding asteroid - Wawrinka comes to net to dispatch a volley but suddenly finds the ball at his bootlaces and can't get it over the net. 30-30.

Stan again targets Federer, sending a smash straight at him to bring up 40-30, and he closes the deal. Fed will serve for it.

Jeff Tarango
Former professional tennis player on 5 live sports extra

Now, I know the Swiss are a peace-loving nation. And yes, yes, these two are great pals, yadda yadda. But if my imagination doesn't deceive me, Stan is going for Roger here. He's trying to foil Fed's sneaky tactic of rushing to net with the not-so-subtle strategy of absolutely leathering the ball at him when he gets there.

It works as he almost takes the racket out of Roger's hand, bringing up 15-30, but Federer gets himself out of trouble with three straight points.

Jeff Tarango
Former professional tennis player on 5 live sports extra

Oh my word. Wawrinka looks to be cruising at 40-15, but he sends a forehand long. Can Federer get to deuce? Wawrinka absolutely nails a smash at 40-30, but Federer, inescapable as time, is there, somehow, and absolutely pings it right off the strings about an inch over the net. Stan is equal to it though and nonchalantly knifes the volley into the open court. That is what Alan Partridge would call liquid tennis.

Jeff Tarango
Former professional tennis player

Federer's usual gossamer touch deserts him at the net as a drop volley sits up for Wawrinka to smack a passing winner past him, and suddenly Stan has 0-40 and three break points.

Federer saves the first two with an ace and a putaway, and he fends off the third with a display of real cojones - following a second serve into the net and painting the sideline with a volley. He closes out a Houdini-esque hold with an ace.

That'll make Stan feel better - absolutely torching a backhand winner past Fed to get to 40-0. That one left scorchmarks on the court. Federer then dumps one into the net and Wawrinka remains in touch.

Jill Craybas
Former world number 39 on BBC Radio 5 live sports extra

Federer may be 34, but there's still some elastic in that serving arm - the ball is clearing the spectators in the first row as it bounces past the flailing Wawrinka. A couple of howitzer deliveries help Federer to a love hold.

Now then, here's the Roger Federer sneak attack that we've been hearing so much about. In case you haven't keeping your ear to the tennis grapevine, Fed has caused a few ripples by charging into the net to take his opponent's serve halfway up the court. It fails the first time, by on the next point it works and Wawrinka nets.

The tactic clearly unsettles Wawrinka and he pings a forehand off the tape and into the tramlines to bring up break point. Wawrinka sends a forehand long, and it's first blood to Federer.

On 5 live, Jill Craybas reckons that you can tell by the way Stan uses his walk, he's a US Open contender, no time to talk. Or words to that effect. He certainly carries a bit of a spring in his step.

But then again the man across the net, resplendent in pink sweatbands today, has never been known for a lack of confidence either. Federer fends off a minor hiccup at 30-30 with a good approach, but then Wawrinka stings him a crisp one-hander down at his toes. Deuce.

Fed sends one into orbit off the frame, and suddenly he's staring down the barrel of a break point. Stan shanks the return, and then sees an ace whizz past him at nostril height. Wawrinka sends a backhand long, and Rog is on the board.

Christopher David:  Currently contemplating how long I stay up to watch this undoubted classic Federer/Wawrinka match.

Woof. Plenty of mustard on the Wawrinka serve, and he's up and running with a simple hold.