Top-seeded Carlos Alcaraz recovered from a slow start to beat Filip Krajinovic 7-6 (4), 6-3 and reach the quarterfinals of the Hamburg European Open on Thursday as Francisco Cerundolo stunned Andrey Rublev 6-4, 6-2. Alcaraz saved four set points down 4-5 in the first set before surging back to beat Krajinovic and improve to 21-2 on clay this season. The 19-year-old Spanish player meets Karen Khachanov for a spot in the semifinals after the Russian beat Fabio Fognini 6-3, 7-5. Cerundolo, ranked 22 places below No. 8 Rublev, is on a seven-match winning streak after taking his first career tour title in Bastad, Sweden, last week. Cerundolo’s next opponent is another Russian — Aslan Karatsev, who won 3-6, 6-3, 6-4 against qualifier Daniel Elahi Galán. In the women’s draw, top-seeded Anett Kontaveit reached the semifinals after Andrea Petkovic retired injured while Kontaveit was leading 6-0, 2-0. Petkovic suspected it was an adductor strain, she said in comments reported by German agency dpa. Kontaveit will next play Anastasia Potapova, who upset 2021 French Open champion Barbora Krejcikova 6-1, 6-3. The other semifinal match pits Maryna Zanevska against American Bernarda Pera. Zanevska beat fourth-seeded Aliaksandra Sasnovich 6-4, 7-5, while Pera swept aside Katerina Siniakova 6-3, 6-1.