Adelaide, Jan 11 : Jelena Ostapenko booked a spot in her first semifinal of the year with a 7-5, 6-3 quarterfinal victory over Marta Kostyuk at the Adelaide International on Thursday. World No.12 Ostapenko of Latvia took 1 hour and 32 minutes to subdue 41st-ranked Kostyuk of Ukraine at the WTA 500 event and improved to 2-0 in their head-to-head (4-0 in sets), WTA reports. The 2017 Roland Garros champion power game was in fine form as she fired 30 winners to 17 unforced errors. Ostapenko's 5-2 first-set lead slid back to 5-5, but she broke Kostyuk's serve three times after that to move to victory. Meanwhile, Daria Kasatkina moved into the semifinals without striking a ball after her quarterfinal opponent, Laura Siegemund, withdrew from their match. World No.15 Kasatkina is now one win away from repeating her runner-up appearance at the second of last year's two Adelaide events. /IANS