Day 5 means crunch—and number crunch—time at the WTA Finals Singapore Presented by SC Global. All four players are in contention as round robin play approaches its conclusion, with multiple semifinal qualification scenarios in play for all. Here’s a breakdown of the matchups.
 Simona Halep (ROU #2) vs.  Agnieszka Radwanska (POL #6)
Head-to-head: Tied, 4-4
Key Stat: Halep will automatically qualify for the semifinals with a straight-sets win on Thursday; Radwanska needs to win in straight sets to have any chance of reaching the semis.
Qualification scenarios abound on Day 5 in Singapore, but each competitor knows that it’s best to focus on playing quality tennis while leaving the math mashups to the media. Simona Halep and Agnieszka Radwanska will be prepared to leave it all out on the court, as it could be the last match of the season for both, and that grim fact should heighten the intensity of their ninth career battle.
Halep has had great success against Radwanska since May of 2013, winning four of five, and the Romanian will look to continue that success by taking advantage of the Pole’s attackable second serve to grab the initiative in the rallies. For Radwanska, who will bid to reach the semifinals with a 1-2 record in Singapore for the second consecutive year, the goal will be to disrupt Halep’s rhythm by feeding her an unpredictable diet of slice, dropshots and angles. When Aga’s on, there’s nobody better at turning a tennis court into her own personal canvas, a place where the unimaginable happens.
Halep will try to deny Radwanska her creative province by keeping her pinned near her baseline with a steady pulse of topspin drives. It’s a strategy that paid dividends for the 24-year-old Romanian last year when she thumped Radwanska, 6-2, 6-2, to reach the finals on her debut at Singapore. If Halep can stick to the plan and provide a repeat performance, the top seed just might be headed for the finals again.
As for Radwanska, she came to Singapore as one of the hottest players in the field. If she can put the disappointment of her two losses behind her and rediscover her form, she may find a way to prolong her season.
Pick: Halep in two
 Maria Sharapova (RUS #4) vs.  Flavia Pennetta (ITA #8)
Head-to-head: Pennetta leads, 3-2
Key Stat: Sharapova only needs to win a set to qualify for the semis; Pennetta qualifies with a straight-sets win.
Maria Sharapova holds a 21-5 record against the Red Group, but Flavia Pennetta hasn’t been buying into the Russian’s mystique of late. The Italian has had the better of Sharapova in their last three meetings, including a 3-6, 6-3, 6-2 victory at Indian Wells this March. After that emotionally gratifying victory, Pennetta gave reporters some insight into what it’s like to try to beat a powerful phenom like Sharapova: “I just try to play the way I always play against her,” she said. “I mean, if you give her time you are dead, so you have to hit the ball, try to be aggressive the most you can, and try to go all the time for the good shot.”
Pennetta has been able to hit her share of “good shots” in their last three meetings, but Sharapova has by no means been left in the dust. In fact, all five of their previous meetings have gone the distance. And with Sharapova suddenly emerging from a long hiatus in mid-season form in Singapore, Pennetta will surely have her hands full no matter how well she plays.
Even if she does earn another win against Sharapova, Pennetta’s career could come to an end on Thursday. If she wins in three sets she’ll be eliminated unless Radwanska upsets Halep in the first match.
With so much hanging over her head, will it be possible for Pennetta to focus on her game and tick off the tactical boxes against an in-form Sharapova? Or is it time for Pennetta’s glorious 2015—and career—to come to an end?
Pick: Sharapova in three
Also on Tap: Chans look to lock up top spot in White Group doubles.
There’s a lot working in favor of Hao-Ching and Yung-Jan Chan. The sisters from Taiwan have won both of their round robin matches and they head into Thursday’s match with Garbine Muguruza and Carla Suarez Navarro needing only a set to lock up qualification. But if they should fall in straight sets, the door will be open for the Spaniards along with the other two teams in the White Group.
Bethanie Mattek-Sands and Lucie Safarova will face Caroline Garcia and Katarina Srebotnik in the final match of the day. The American-Czech duo own a 3-0 lifetime edge over their opponents, and can lock up a semifinal berth with a win.