MELBOURNE, Australia (AP) — Serena Williams has withdrawn from a semifinal match against top-ranked Ash Barty in an Australian Open tuneup event. Williams beat Danielle Collins 6-2, 4-6, 10-6 in the quarterfinals and later said she was looking forward to a test against the current No. 1. She later pulled out citing a right shoulder injury to give Barty a walkover into the Yarra River Classic final. The Australian Open starts Monday. Germany edged defending champion Serbia for a place in the ATP Cup semifinals with Alexander Zverev recovering from a singles loss to top-ranked Novak Djokovic to beat him in the deciding doubles.