Of the four women playing the Australian Open semifinals on Thursday, Sloane Stephens, Victoria Azarenka, Maria Sharapova, and Li Na, only Li played at or above her usual standard.
Azarenka defeated Stephens 6-1, 6-4, but only after 31 unforced errors to 21 winners and a controversial, 9-minute injury time-out right before Sloane served to stay in the match and lost, arguably in part because of such a long cooldown. Sloane's play was extremely spotty, though, with 42 unforced errors to 14 winners. Both were highly vulnerable on second serves; Victoria defended only 37% of hers, Sloane 30%.
Li's 6-2, 6-2 victory over Sharapova was of much better quality. Maria always competes well, and she didn't play that badly against Na, but while Maria almost always hits harder and deeper than her opponents, Na surpassed her in power and depth while making many fewer errors. Maria had 32 unforced errors to 17 winners, whereas Na was the only one of the semifinalists with a positive balance: 18 unforced errors to 21 winners.
In terms of stroke production, one of the most interesting shots to observe in the semifinals was Sharapova's topspin-slice first serve, on which she gets a impressively pronounced slice component. She hit quite a few serves where the sidespin alone made the ball curve as much as six feet to her left, but unlike a pure slice serve that curves sharply but can't be hit as powerfully, Maria's first serves also have a significant amount of topspin to push them down into the box.
Photo Stroke Studies: