(23) Sabine Lisicki vs. Kaia Kanepi
First meeting

What Lisicki needs to do to win:

The biggest challenge for Lisicki will be avoiding an emotional letdown. Against a fellow big-hitter in Kanepi, she will have to use the same weapons that allowed her to upset Serena. Liscki’s wide serve in the deuce court is especially dangerous. She will also have to return well and avoid the temptation to try to blast Kanepi off the court.

What Kanepi needs to do to win:

Kanepi is coming off upsets of No. 7 seed Angelique Kerber and British favorite Laura Robson, so her confidence will be sky-high. Her serve is somewhat erratic; she needs about a 70 percent first-serve conversion rate to boost her chances. If she has a good day going at the notch (her body serve is especially effective), she could hold to put a lot of pressure on Lisicki’s seve.

The Pick: Lisicki in two sets

Lisicki loves Wimbledon. When your love for one tournament has been requited, you don’t crumble under pressure—you embrace it. Lisicki’s improved mobility will be the difference in this match. You have to like her chances if it becomes another three-set marathon (like her match with Williams), but all that firepower ought to be more than enough to see her through in two close sets.

(4) Agnieszka Radwanska vs. (6) Li Na
Li leads head-to-head 6-4

What Radwanska needs to do to win:

The surest way to handle Li is to apply constant pressure and hope that her focus wavers—as it so often does. That means scrambling and playing excellent defense against the relatively flat shots of Li. Holding serve is often an adventure for Radwanska, but the grass courts help her cause, giving her opponent a lower bounce, which makes it harder to hit an aggressive return.

What Li needs to do to win:

Given the stakes and the opportunity—both women know they’re the best players left in the field, and neither has won this tournament—Li has to handle the pressure without withdrawing into herself as she sometimes does when in a position to win. She must serve well and take charge once the ball is in play. On defense, Li must capitalize on Radwanska’s relatively weak serve.

The Pick: Radwanska in three sets

This could be a wonderful, tense and long match, given both Radwanska’s inability to overpower anyone and the fact that no lead is big enough for Li to blow. Radwanska has made a great deal of progress on grass since losing to Li at Wimbledon in 2010. It’s hard to see Li smothering Radwanska’s game of flat groundstroke bullets with the kind of consistency it would take to win.

(17) Sloane Stephens vs. (20) Marion Bartoli
Bartoli leads head-to-head 1-0

What Stephens needs to do to win:

Use her spins to create sharp angles and stretch Bartoli. Stephens’ variety and court coverage are major assets in this match. She must use her topspin to force Bartoli, who has restricted reach playing with two hands off both wings, into running replies. Stephens will want to mix up her serves and use the body  serve to tie up Bartoli, who is a terror on returns.

What Bartoli needs to do to win:

Control the center of the court, take the ball early and fire into the corners to force Stephens to defend. The 2007 Wimbledon finalist’s flat blasts stay low on the lawn, so she can back Stephens off the baseline. Bartoli likes to go big off both first and second serves, but she has hit a tournament-high 21 double faults. She must pick her spots on serve and diminish her donations of double faults.

The Pick: Stephens in three sets

Stephens is the faster, fitter and more versatile player. Their lone prior meeting went three sets and this could go the distance as well. If Stephens plays dynamic tennis, employs all of her shots and avoids lapses into passive play where she relies on her speed solely to counterpunch, she should reach her second Grand Slam semifinal of the season.

(8) Petra Kvitova vs. (20) Kirsten Flipkens
Flipkens leads head-to-head 2-1

What Kvitova needs to do to win:

It’s always the same for this baffling, hugely talented 6-foot lefty and former Wimbledon champ from the Czech Republic: Keep down the ghastly unforced errors and serve well. Kvitova will have to find a way to take command with that wicked, lashing forehand, especially in Flipkens’ service games, to keep her Belgian opponent from jerking her all over the court.

What Flipkens needs to do to win:

Flipkens’ first assignment will be to control her nerves. After all, she’s playing for a semifinal berth in what has become a wide-open Wimbledon. She’s having her best year, thanks to an extremely versatile game. She’ll need to poke back Kvitova’s big lefty slice serves. She’ll also need to chip, slice and mix up the pace  to frustrate her tall and still somewhat gangly opponent into errors.

The Pick: Flipkens in three sets

Pundits have been burned before ppurpleicting big things from Kvitova. Sure, some champions are slow learners and need more time than others to adjust to the pressure of their status. But Kvitova has been dithering for too long, and she can’t be trusted. Flipkens has won both tournament matches they’ve played, yet all of the pressure will be on Kvitova, and that’s something she has rarely been able to handle.