Stosur loses in Dubai tennis quarters Australian Samantha Stosur lost to doubles specialist Roberta Vinci of Italy 6-2 6-4 on Thursday in the quarter-finals of the Dubai Championships. The 2011 US Open champion made 28 unforced errors and was broken twice in each set. Despite the latest setback, the 28-year-old said she felt she was improving over her dismal start to the year. Former world No.1 Caroline Wozniacki reached the semi-finals with a 4-6 6-1 6-4 win over Marion Bartoli, shrugging off a code violation in the process. Wozniacki was warned for illegal coaching as the match boiled up to a thrilling finish, apparently because she was talking to her father Piotr. Wozniacki will tackle Petra Kvitova for a place in the final after the 2011 Wimbledon champion underlined her new status as the unofficial tournament favourite by ending the title defence of Agnieszka Radwanska. The Czech player again showed she is in her best form since winning her only grand slam title 19 months ago, out-hitting and out-serving the third-seeded Pole 6-2 6-4.