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Kei Nishikori and Novak Djokovic have both slipped down the rankings over the last 12 months due to injuries.

They're both big-match players. Djokovic needs no introduction with 12 Grand Slams to his name.

Nishikori is appearing in his eighth Slam quarter-final and was runner-up at the US Open back in 2014.

Andy Murray
Two-time Wimbledon champion on BBC One

Roger is playing well and moving well, and against Anderson he leads 4-0 in their head-to-head. So I feel comfortable he would get through.

It would take an unbelievable serving performance from Anderson. If he serves 80% first serves and Roger has a really bad serving day, then he might have a chance.

Jonathan Jurejko
BBC Sport at Wimbledon

Roger Federer is making an unfamiliar journey from the locker room today - to Court One.

It will be the first time he’s played here since the 2015 quarter-finals.

The Wimbledon stewards are expecting a full media area (which is not usually the case) as they urge everybody to budge up towards the end of their rows.

Here’s Roger! He’s found his way here.

Image source, BBC Sport

Pat Cash
Former Wimbledon champion on BBC TV

I thought in the first three rounds, he may have struggled a little against Mannarino, but I have never seen him play better. How is he still going at 36? I have never seen him play better.

His movement, the shot selection, the variety. He is playing like it is an exhibition, He never gives one shot the same.

Novak Djokovic and Kei Nishikori both make their way down the shiny steps to Centre Court, past the men's singles trophy which Djokovic has already won three times of course.

Will we see Novak as pumped as he was against Kyle Edmund in round three today?

Image source, Getty Images

Roger Federer's progress through the draw has been smooth and serene, not dropping a set nor losing a service game on his way to an Open era record 53rd Grand Slam quarter-final.

Another straight-set win over Kevin Anderson will see the Swiss great better his record run of 34 consecutive sets at SW19, which he enjoyed between the third round in 2005 and the final in 2006.

"I don't think it's something anybody aims for, to win every match in straight sets," Federer said.

"I hope I get off to a good start, go from there. If it happens, it happens."

Saj Chowdhury
BBC Sport at Wimbledon

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Former Formula 1 champion Nico Rosberg is spending his Wednesday at Wimbledon. He was philosophical when I asked him about his own country's display at the World Cup and then gave his semi-final prediction.

Take it away Nico...

"The mood was bad in Germany, but they didn't deserve to remain in there," he said. "They wouldn't have won the tournament anyway.

"We're hoping for an England v France final - that would be really exciting. Hopefully, that will happen on the day of a Nadal v Federer final, 10 years after 'that classic'.

"My prediction for later? England will beat Croatia 2-1."

Pat Cash
Former Wimbledon champion on BBC TV

Boy has Anderson got a serve. I have got a lot of admiration for him. I thought he was another big loping guy who has a big serve.

But he has been to the final of the US Open, in the top 10 regularly, got a big serve, big forehand, works hard and volleys well.

He's a good all round player, and to win tie-breakers like he has shows how good he is under pressure.

Boris Becker
Three-time Wimbledon champion on BBC TV

They are playing on Court One, which is more Anderson territory.

Roger is used to playing on Centre Court. Court One is a different court, different atmosphere, different bounce. Anderson played there for four hours against Monfils so he is used to it.

Roger is out of his territory. The beginning of the match is big for Anderson to say 'this is my court'.

And Anderson does register on the list of most aces at Wimbledon in the men's draw this year, although John Isner and Milos Raonic - who meet later - are the top servers left in the competition...

Image source, BBC Sport

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Eighth seed Kevin Anderson has not won a set against Roger Federer in their four previous meetings.

The South African is through to the last eight at Wimbledon for the first time.

"Playing somebody like Roger Federer is going to be a great experience," he said.

"Not just an experience, but a challenge that I've set for myself. I feel like a lot of aspects of my game can give him a lot of trouble."

Pat Cash
Former Wimbledon champion on BBC TV

It doesn't get any better at this stage of the tournament. You are very excited about potentially going through, you know you are up against the best players in the world. You navigated the first week, you are in the business end and a win is a priority.

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Next up for Novak Djokovic is a quarter-final against Kei Nishikori, who he has beaten 12 times in a row since the Japanese star claimed his biggest victory in the semi-finals of the US Open in 2014.

But this will be their first meeting on grass.

"I think it's going to be a new game for us," said Nishikori.

"He's always like a big war for me. Maybe I don't have a good record with him, but I always enjoy playing him."

How did Novak Djokovic rediscover his mojo?

Our man Saj Chowdhury did some digging. Have a read here.

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Andy Murray
Two-time Wimbledon champion on BBC One

In terms of his level and the way he's playing, I think Novak is back to where he wants to be. Mentally he looks where he needs to be - looks fired up and motivated. He's got a great shot.