Tokyo: Top-ranked Maria Sharapova retired during the second set of her Pan Pacific Open semi-final with a hamstring injury on Saturday.Second-seeded Martina Hingis will now face Serbia's Ana Ivanovic in the final.After dropping the first set 6-1, Sharapova consulted with her trainer. She won the first game of the second set before retiring. "It's disappointing to have to finish this way," Sharapova said. "I started to feel pain in the second game of the first set. I tried to go on, but you can't get away with it when you are playing against a top player".Hingis posted a 6-4 6-3 win over defending champion Elena Dementieva of Russia to reach the final.Sharapova, who reclaimed the No 1 spot in the WTA Tour rankings on Monday, lost to Serena Williams in the final of last week's Australian Open.The Russian had 17 double-faults in her first match against Italy's Francesca Schiavone and doube-faulted 14 times in the quarterfinals against Ai Sugiyama of Japan on Friday.