Image source, Getty Images

• 35 years old
• Six months out of the game
• Into the last eight

They're all just numbers, to be honest. There's something about Roger Federer that is non-quantifiable.

Only the tennis Gods have the means to measure him up.

That's it from our live coverage today.

Don't forget that British number one Johanna Konta is in last-16 action in the early hours of the morning - around 02:00 GMT.

Join us for radio and text commentary.

Roger Federer will face world number 50 Mischa Zverev in the quarter-finals, after the German stunned top seed Andy Murray earlier.

"I watched that match when I came into the building. I watch a lot of tennis when I'm on tour. Tennis is on TV non-stop. I thought it was an incredible match.

"I couldn't believe it. Mischa has a good game coming forward. He was going for it and deserved the win. It was a tough one for Andy but he'll be back."

Roger Federer after beating Kei Nishkoi: "It was a great match and a joy to be part of it

"I wasn't playing badly in the first set - it's a quick court and things happen fast. It was about staying calm at 4-0.

"I thought it cant get any worse from there. It was hard not to win that first set after all the effort but it paid off in the end. This is a huge win for me in my career."

Nishikori returns into the net.

The crowd get a bit too boisterous and need to be hushed.

A serve out wide has too much juice for Kei.

Is the next one an ace? Called out. Federer challenges and it was in! Match point.

Nishikori is going to make Federer earn it on his own serve.

Federer finds the net for the hold.

Federer doesn't give Nishikori a sniff with four un-returnable serves.

The 17-time Grand Slam winner is one game away from the quarters.

Nishikori's having more ups and downs the Alps right now.

He looks on course for a break of serve as he drifts to 15-30 but some quickfire net play has him back up to 40-30.

Up and down on the baseline like a yo-yo before Federer puts him out of his misery with a forehand.

And then he bounces back again to clinch the hold.

Serve and volley from Federer - sort of. Is there anything this man can't do?

Maybe... as he volleys into the net.

Ace number 22 for the Swiss and a superb forehand down the line, eradicating the spin, for the hold.

The last thing you want when you've got a sore back is to be battered around the baseline - but that's what happens for the first two points.

Nishikori shakes it off though and is at the net to volley his way back to 30-30.

Backhand up the line opens the space for Federer to forehand into the corner for break point.

Nishikori saves - deuce. My word, Federer picks up a slower serve and ziplines it crosscourt into untouchable territory.

The Japanese some how claws it back though and Federer goes long with the return.

He's back on his feet. The roar goes up for Federer, who is three games away from the quarters.

Go stretch the legs. Talk to your family. Have a go at the crossword.

Kei Nishikori has a medical time out to receive more work on his back.

Federer looks to be on the back foot but pulls out a forehand chopped slice that has Nishikori wondering what day of the week it is.

Kei collects himself and rifles a forehand return down the line.

Ace number 21 for R Fed and a serve down the middle clinches the hold.

Federer has dipped his forehand in Tabasco sauce, finding extra, wicked whip that Kei can't handle.

Two break points, the first goes, but the second is drummed into the net by Nishikori.

Andi: Watching Federer is like watching your local butcher carving up meat but credit to Kei for hanging on. Amazing tennis.

Zach: Gutted that Murray is out but hopefully it can be a Fed v Nadal final once again. 

Put the coffee on. It's the final stretch.

Speaking of stretching, Nishikori has the trainer out to do some work on his back, the Japanese flat on his back on the blue Plexicushion.

The world number five has risen like a phoenix in the last half an hour and draws a "come on!" from Federer who is now trying to re-impose himself.

The Swiss is taken to deuce, but serves his way out of the cul-de-sac.

Federer flutters a backhand into the net, can only hit a return into the ground, goes wide down the line and then backhands out of bounds for an undramatic hold and set for Nishikori.

We're going all the way, folks.

Image source, Reuters

Pow-zap-thwack serving from Federer to ace his way through a love hold.

Can Nishikori serve out the set?

Nishikori outlasts Federer punch for punch on a baseline rally to hold to 30 and he's a game away from the set.

Obasse: Come on Federer. at 35 you are still far better than so called top 10 players. 

John: I'm 45, have 18 month old twins & I'm physically destroyed, Federer has 2 sets of twins & he looks like a spring lamb! Legend.