MELBOURNE, Australia — Stan Wawrinka added a win over Rafael Nadal to his list of firsts in a stunning run to his maiden Grand Slam title, extending his rival's injury-cursed run at the Australian Open with a 6-3, 6-2, 3-6, 6-3 upset in Sunday's final. The 28-year-old Wawrinka had never taken a set off Nadal in 12 previous meetings, but attacked from the start against the 13-time major winner and regained his nerve after dropping the third set against the injured Spaniard. Nadal appeared to be on the verge of retiring in the second set, when he hurt his back and needed a medical time out, but he refused to quit.