The second seed John Isner is the first big casualty from the Sydney International men's draw after losing to fellow American tennis player Bobby Reynolds.
In a setback to his Australian Open hopes, the 17th-ranked Isner succumbed 3-6 6-4 6-4 in the second round at Sydney Olympic Park.
Crowd-pleasing women's world Number 10 Andrea Petkovic has withdrawn from the Australian Open with a stress fracture of her lower back.
