The Scot lost in straight sets to the South African, dashing his hopes for a third consecutive Canadian Masters title.
“I just felt very slow. The game seemed to be going so fast,” Murray said. “It's happened to me already once this year. I've trained really hard to get ready for the tournament. I've always played very well here.
“I started both sets really, really badly which doesn't help against someone that serves like Kevin. “
Murray will play doubles alongside his brother Jamie tomorrow, before beginning preparations for next week’s Cincinnati Open.