Denis Istomin has pulled off a first-round upset at the Rogers Cup in Montreal by beating Janko Tipsarevic in straight sets.
The Uzbek, ranked number 66 in the world, was a convincing victor over the Serbian, who has won four ATP World Tour titles in the past 18 months.
Tipsarevic fell behind early in the opener and from then on, Istomin was relentless and presented his opponent with few chances to get back into the set.
He went on to take it 6-4, and was equally clinical in the second, producing a number of back-court winners on his way to tying up the match.
Istomin will face the winner of Jarkko Niemenen and Kei Nishikori in the second round.
