Maria Sharapova outlasts Kerber in three sets to reach Porsche finals STUTTGART, Germany, April 27 (UPI) -- Top-seeded Maria Sharapova outdueled Angelique Kerber Saturday to reach the finals of the Porsche Tennis Grand Prix in Germany. Sharapova, the defending tournament champion, struggled with her serve at times against the third-seeded Kerber but prevailed 6-3, 2-6, 7-5. Sharapova will face China's Li Na, the No. 2 seed who topped American qualifier Bethany Mattek-Sands 6-4, 6-3. Li served three aces and won 68 percent of her first-service points.