Hawkeye's heat map, court positioning, rally direction - have another look at the round robin match between Li Na and Sara Errani from a statistical perspective, right here!
WTA Staff

China's Na Li loves to demolish the ball when it sits sweet in her strike zone right off her waist.

Her flat forehand in particular is the preferred weapon of choice when it's time to pull the trigger and put the point to bed.

But problems arise for Li when her opponent gets the ball lower or higher out of her strike zone - a talent her Italian opponent tonight, Sara Errani, just happened to be very good at.

Li ultimately defeated Errani, 63 76(5), but things got very interesting late in the match with Li twice failing to serve it out at 5-4 and 6-5. Li trailed 3-1 early in the second but it was the strength of her forehand that helped her regain the lead. And then it started misbehaving - badly.

Li's forehand dominated the back of the court with 17 winners (Errani had seven) but there is a dark side to her ultra-flat forehand - SAP analytics uncovered 14 unforced errors and another 12 forced errors that Errani extracted mainly with the pressure of height - both low and high. Errani hit 56% of her groundstrokes to Li's backhand mainly staying away from the strength until an opportunity developed to really pressure it.

Serving for the match at 5-4, Li quickly went down 0-40 but then stepped up her aggression as most players do with their back to the wall. Now at deuce, Li misfired again as she went for too much on a low, wide forehand that landed well wide. Hitting the ball around knee height or lower suddenly became a big problem. Li missed another low shot, this time a backhand, into the net and a fairly routine second set now had alarm bells ringing.

Li did break back for a 6-5 lead but the height issue quickly popped up again. Li missed a low forehand approach on the first point and then missed an almost identical ball in the middle of the court on the following point - except it was higher out of the zone this time. Li became tentative in the pressure situation and Errani stepped in and crushed a return winner to get things back even again and force a tie-break.

Fortunes were quickly reversing as Errani led 3-1 in the breaker but Li pulled things together to avoid a potentially disastrous second set collapse to win the match in straight sets.

Li's power game gave Errani little choice but to stay back and defend. Hawk-Eye visualization showed Errani contacted her shots 92% of the time behind the baseline and only 8% inside for the match. Li played 67% behind and 33% inside as she kept mounting offensive strategies based on power and direction.

The opening set was tight early until Errani threw in an untimely double fault at 2-3 to donate the first break of serve. Errani had a chance to break back immediately in the next game but Li crushed a first serve down the T at 30-40 that Errani returned with a slice forehand that floated past the baseline and danger was averted.

Errani had an easy hold to love down 5-2 and Li again found herself in danger down 15-30 leading 5-3. Li stepped up with her first serve and rocked an ace out wide through the line that was unsuccessfully challenged by Errani. Li closed the set out with a big approach to Errani's forehand wing and finished off the ensuing overhead.

What got the match close were the different types of points each player was chasing, or attempting to force on their opponent. Li hit a bruising 42 winners to Errani's 14 for the match but also accumulated 35 unforced errors to the Italian's 13. Different ways to earn a paycheck is what makes this sport so great.

First up at 5pm tomorrow night Li will now play Jelena Jankovic, who played great in defeating Victoria Azarenka in today's second match. Li will have to lift her game a notch or two if she is defeat the improving Serb.

Craig O'Shannessy is an Australian tour coach who studies matches to uncover the patterns and percentages that dominate the game. He runs a tennis academy in Austin, Texas and a website called www.braingametennis.com.