Janko Tipsarevic was made to work hard but eventually defeated Marcel Granollers to book his place in the Rogers Cup semi-finals.
The Serb was taken deep into the first set by Granollers but found a late break to win it narrowly 6-4.
Granollers tried to fight back but the second set followed a similar pattern, Tipsarevic again needing a single break to wrap up the match 6-4 6-4.
Fifth seed Tipsarevic now faces a potential semi-final with countrymen Novak Djokovic, who takes on German veteran Tommy Haas in a quarter-final clash later today.
