Three-time grand slam champion Stan Wawrinka is an Australian Open second-round casualty with a heavy loss to unseeded American Tennys Sandgren.

The ninth seed, who was late to declare his fitness for the grand slam he won in 2014, had no answer to the in-form Sangren on Thursday night in a 6-2 6-2 6-4 defeat.

Heading into Melbourne Park, the Swiss veteran hadn’t played a competitive match in six months after suffering a serious knee injury.