Maria Sharapova is a strong contender for the person you would most want by your side in the trenches. The Russian, backed up to the cliff edge, responds with the aggression of a lioness protecting her brood.

Stinging forehand power sets up 15-40 and then a beautifully controlled stretch volley converts the first of two break points.

BBC Sport's Stephan Shemilt on Court One

Image source, Getty Images

"This is barely believable. With Tommy Robredo netting and shanking, Roger Federer broke to love in the first game of the second set. The crowd, expecting something of a contest, have gone from admiration to a sort of murmured embarrassment. After another blink-of-an-eye Federer hold, a frustrated Robredo gets on the board to warm applause."

Maria Sharapova keeps her cards on the table as she holds serve comfortably. Kerber to serve for the set next and a timely graphic from the BBC Two coverage shows that German has peppered Sharapova's backhand off tee-off.

All but two of her serves have been to that wing.

Germany's Sabine Lisicki recovers from an injury scare to book her place in the quarter-finals with victory over Yaroslava Shvedova of Kazakhstan on Courth Three. The 19th seed will face third seed Simona Halep in the last eight. That should be a belter.

Not a quiver, not a waver from Angelique Kerber who races to 40-0 and doesn't flinch as Maria Sharapova nicks a point.

The German tugs the ripcord on the game with a big serve down the middle that a stretching Sharapova can get only a flick of frame to.

Maria Sharapova's serve is purring now. She motors away to a hold to love. All very well, but she needs a break if she is going to get something from the set.

Kerber will get fresh ammunition as they open a can of new balls at the end of the game.

Lindsay Davenport
1999 Wimbledon champion on BBC Two

"Besides that opening service game, Maria has looked comfortable but what surprises me is her returning game, she has not got her return going yet."

Angelique Kerber is doing shuttle runs, side to side, back and forth, to stay in the point at 15-15. There is something in international law about cruel and unusual punishment isn't there? This treatment from Sharapova might fall under that category.

The German has her revenge though as Sharapova bunts the final wrong-footing backhand a little long.

BBC Sport's Stephan Shemilt on Court One

Image source, Reuters

"Two Tommy Robredo forehands dumped in to the net give Roger Federer a second break, with the third seed sprinting through another hold to win the first set in 22 minutes. 22! With the quarter-finals scheduled for tomorrow, the seven-time champion is eyeing maximum time off. They may have space for more than the scheduled three matches on Court One."

Maria Sharapova starting to do the maths on this one. The Russian's serve looks like it has been stiffened by a tactical rethink. She is still within striking range in the set.

Image source, Reuters

Something slightly spooky about this photo don't you think? Warbler Katherine Jenkins stares down the lens, locking the viewer in a personal moment amid the hub-bub of Centre Court. Get on the blower to the National Gallery and clear some hanging space.

Meanwhile on court, Angelique Kerber racks up her first ace on the way to a hold for the loss of just one point.

BBC Sport's Stephan Shemilt on Court One

"Despite the warm sunshine, Court One is far from full as Roger Federer and Tommy Robredo belatedly begin their second week. A swish of the headband and Federer holds to love inside one minute and is already commanding the fourth-round match with a healthy first-set lead."

Image source, Reuters

The ball toss is shaky, the forehand is wobbly, but the instinct to find her way home through the ups and downs of a game is as keen as ever.

Maria Sharapova plants an ace on the apex of the service box to take the game for the loss of two points and get on the board.

Angelique Kerber is happy to sit on the baseline and trade, trying to get her forehand into play.

It is almost at though the German has her toes nailed to the whitewash as she sits down to scoop back a groundstroke on her way to saving break point from deuce.

Sharapova has not quite crunched the numbers on this conundrum yet. Uncharacteristically high error count as she allows Kerber to slip through her grasp.

Image source, Getty Images

Sabine Lisicki called for the trainer early in the third set for what seems to be a problem with her neck and shoulders but seems to be moving freely enough now and has traded breaks of serve with Yaroslava Shvedova.

You can watch that match by clicking on the Live Coverage tab above.

Today's vote is now live on this page and the question of the day, as the women's quarter-finals get under way, is this: Who will win the most Grand Slam titles out of Eugenie Bouchard, Simona Halep, Madison Keys, Alize Cornet, Laura Robson and Heather Watson?

You can send us your views via the usual means of #bbctennis on Twitter, text on 81111 (UK mobiles) or the BBC Sport Facebook page., external

The vote will close at the end of this match between Maria Sharapova and Angelique Kerber.

Angelique Kerber's forehand is a clubbing shot and the German 26-year-old hammers a low one over the net and down the line for a winner and 0-30.

More of the same from Kerber. Hitting the ball with a real bosh as she opens up 15-40 and two break points.

The cogs are whirring upstairs for Maria Sharapova. How to get out of this one? A big forehand of her own steals back one of the break points, but opting for serve power in pursuit of the other was the wrong call.

Double fault and first blood Kerber.

The head-to-head record is 4-1 in favour of Maria Sharapova, Angelique Kerber's only win coming back in 2012 in Paris.

This is their first encounter on grass though. Sharapova to serve...

Meanwhile Court One are giving Roger Federer a big welcome as he steps out to face Tommy Robredo.

Waves all around the bowl from the seven-time champion.

You can watch that one at the top of this page or on the red button on your telly.

The category missing from this little game of tennis top trumps is mental strength and stomach for a fight.

Sharapova would max out the rating on either.