No. 2-ranked Iga Swiatek lost to a player younger than 18 for the first time on tour when she was stunned by Mirra Andreeva in the Dubai Championships quarterfinals on Thursday. The 17-year-old Andreeva won 6-3, 6-3 to become the youngest semifinalist in Dubai's 24-year history. Swiatek took their only previous match last August in Cincinnati, losing the first set and winning 7-5 in the third.