It's exciting to see Sam Stosur (#24) of Australia play well again in the grand slam stage. It has been 4 years since she last reached her last semi-final here in Roland Garros. And this is definitely a surface she loves to play in. She was a finalist here after all, in 2010.
She's had to defeat a lot of very good players to reach this stage:
R1: Misaki Doi (JPN) (#42) 62 46 63
R2: Zhang Shuai (CHN) (#69) 63 64
R3: Lucie Safarova (CZE) (#13) 63 67(0) 75
R4: Simona Halep (ROU) (#6) 76(0) 63
On paper, she has a 3-1 head-to-head over Tsvetana Pironkova (#102) of Bulgaria, so she is the expected one to get the semi-final slot on her side of the draw.