Former US Open champion Dominic Thiem has withdrawn from the Winston-Salem Open due to gastroenteritis.
 
World No. 82 Thiem was looking to make his first appearance of the North American hard-court season and first outing since reaching the Kitzbuehel final earlier this month.
 
The Austrian was due to play his first-round match tonight against Frenchman Arthur Rinderknech. American Omni Kumar replaces Thiem in tonight's match.