Top-ranked tennis player Jannik Sinner is “very confident” that he will avoid a doping ban after the World Anti-Doping Agency appealed a decision to clear him of wrongdoing following two positive drug tests. The Montreal-based body known as WADA announced Saturday that it is seeking a ban of one to two years for the U.S. Open champion and has appealed to the Switzerland-based Court of Arbitration for Sport (CAS). “I’m still surprised but I will collaborate like I did before,” Sinner said Friday, the day before his first match at the Shanghai Masters.