Jankovic, seeded eighth, ousted No. 4-seeded Samantha Stosur 6-4, 6-2. Jankovic was good on just 52 percent of her first serves but still managed to win two-thirds of the points on serve and only lost her serve once.
She had four breaks in the eight games Stosur served.
Fifth-seeded Agnieszka Radwanska had the easiest time in the quarterfinals, dispatching Sabine Lisicki 6-2, 6-1 in 66 minutes. Radwanska took nearly two-thirds of the points in the match.
Julia Goerges rallied for a 4-6, 6-3, 6-4 victory over Daniela Hantuchova in a 2-hour, 15-minute battle. Georges managed two breaks in each set.
Friday's semifinals have Goerges going against Wozniacki while Radwanska plays Jankovic. Goerges won the last two times she's played Wozniacki and evened their series at 2-2. Radwanska and Jankovic have split their two previous meetings.