NEW YORK — Caroline Wozniacki trusts her stamina so much that she plans to return to New York in two months to run a marathon.Maria Sharapova, usually the one wearing down opponents in the third set, sure couldn’t keep up on a steamy Sunday at the U.S. Open. Wozniacki won 6-4, 2-6, 6-2 in 2 hours, 37 minutes to get back to her first Grand Slam quarterfinal in more than two years — and get back in the headlines for reasons other than her personal life."The season for me has been a little bit up and down," she said in quite an understatement, "and it’s so nice to kind of start feeling like I’m playing the way I want to."Because of the heat, the players received a 10-minute break before the final set; Sharapova returned to the court late, arguing with the chair umpire after receiving a time violation warning. Perhaps sensing that she was fresher than the five-time major champion, Wozniacki later complained that Sharapova was dawdling between points.Her tardiness seemed to swing the Arthur Ashe Stadium crowd’s support squarely in Wozniacki’s favor.