Take a look at Quarterfinal Friday's first match - Li Na's encounter with Sara Errani - but this time from a much more statistical perspective, thanks to Craig O'Shannessy and SAP Analytics.
WTA Staff

Sara Errani used the partisan energy of her home crowd and a patient, grinding game plan to score the biggest win of her career to advance to the semifinals of the Internazionali BNL d'Italia in Rome.

Errani defeated World No.2 Li Na 6-3, 4-6, 6-2 by weathering the storm of winners to make Li feel the pressure of her consistency, particularly through the ad court at Li's erratic backhand.

Errani does not possess near the firepower of her higher-ranked Chinese opponent but through a combination of playing on a slower clay court in front of a raucous home crowd and constantly scraping one more ball back in play she was able to beat Li for the first time in seven attempts.

It was simply a numbers game for Errani as she could not completely stop Li from thumping big winners all over the court - she just had to minimize the damage. The difference for the Italian was how many errors she could extract with big play of her own mixed with annoying her opponent with lightning fast feet, outstanding defense and using the energy of the crowd to carry her to the finish line.

Ad Court Dominance
Li blasted 14 backhand winners for the match, including six in the third set, as she stuck to her aggressive game plan to try and keep points shorter and more powerful against her nimble opponent. SAP analytics showed Li struck 11 of the 14 backhand winners down the line with her signature shot but Errani persisted to attack deep to the ad court to make Li as uncomfortable as possible with depth and spin. It was a masterful plan as Li committed 33 backhand errors trying to go for too much too soon to escape the web of control that Errani was weaving in the ad court.

Secondary Redirect To The Forehand
Once Errani established control in the ad court she would strategically switch tactics at opportune times to attack Li's forehand, extracting 25 errors over three sets. Errani's backhand down the line in particular did the most damage. With Errani serving at 4-3, 40-15 in the opening set, she controlled the ad court with patient backhands and Li tried to get out of the pattern with a big backhand down the line. Errani countered cross court and two shots later hit a slow, heavy backhand slice crosscourt to Li to remove the power from the point and frustrate her opponent. Li defiantly crushed the backhand crosscourt from inside the baseline but in turn handed Errani the necessary power to hurt Li down the line to her forehand as she was now out of position to defend and netted the defensive attempt. Cat and mouse tactics like this one played out again and again for over two hours until patience ultimately triumphed against power.

Backhand Down The Line
Errani's backhand withstood the brunt of the power from Li's powerful groundstroke and hit four big winners for the match - all coming on a game ending point.

Set 1: Errani Serving 2-1, ad out: A huge backhand down the line winner from a crosscourt backhand from Li after running Li side to side earlier in the point. It was an early statement about who was controlling the points.

Set 1: Li Serving 3-3, 0-40 - Errani stayed in the point with a wide defensive, squash-like forehand slice down the line and Li approached cross to the backhand where Errani slid perfectly in an open stance to rifle a backhand winner down the line.

Set 2: Errani Serving 1-1, 40-15 - Li had a run-around forehand in the ad court and punished it cross court, pushing Errani wide and well behind the baseline. Errani pulled the trigger in spectacular fashion for a clean winner right on the line that Li had no chance to run down.

Set 2: Errani Serving 4-4, 0-40 - Li had worked her way towards the net and approached with a backhand crosscourt but Errani knew exactly where it was going and was in the ad court waiting for it, directing a passing shot past Li who was stuck in the middle of the court.

Errani stayed mentally strong through all three sets while Li's mind and game seemed to ebb and flow. Errani won 15 of the last 16 points of the opening set and 14 of 17 of the third set.

Craig O'Shannessy (@BrainGameTennis) is the leading analyst for wtatennis.com throughout the 2014 season, utilizing SAP Data & Insights to uncover the patterns and percentages that dominate the game. Visit Craig's website at www.braingametennis.com for more expert strategy analysis.