The British number two booked a last-eight meeting against Slovakian Dominik Hrbaty in the Rogers Cup in Montreal by beating Croatia's Mario Ancic 6-2 3-6 6-2.
The 1997 US Open finalist overcame a casual drop-volley which ultimately cost him the second set to see off Ancic, who knocked Tim Henman out of Wimbledon in 2004, and put it down to renewed self-belief in his biggest weapon.
"That's when I play my best tennis - when I have the confidence to hit my first and second serve and not worry about the consequence of hitting a few double-faults," he told Sky Sports.
"If you look at the great players like Pete Sampras they went after their first and second serve as hard as they could and when I am confident and playing well that's what I do, and I am just sticking to it no matter how it goes out there.
"I have never beaten Mario before and Mario is an up-and-coming player so I was really, really pleased I managed to get through that," Rusedski added.
"I had one bad shot that could have cost me the match but I played a really solid third set."
Rusedski cruised through the first set in just 39 minutes. Combining powerful serving with a deft touch at the net, he gained the edge over Ancic.
The warning signs were there for Ancic from the off as he lost his opening service game.
The Croatian threatened a comeback by holding four break points in the fourth game but Rusedski simply upped the tempo on each occasion despite some fine returns from his opponent.
The big-serving left-hander managed to hold for a 3-1 lead and then all but clinched the set with a second break.
Ancic had a further opportunity in the sixth game but was unable to convert.
The second set continued in a similar vein with Rusedski looking in charge before a moment of complacency altered the complexion of the match.
Holding game point to make it two-all, Rusedski had the entire court in which to place a simple forehand volley. But even though Ancic had given up, turning his back on proceedings, the British number two tried to be too clever and dumped his drop volley into the net.
Two fine returns quickly handed Ancic a break point which was converted when Rusedski double-faulted.
Rusedski was shell-shocked and he failed to pick up a point on the Ancic serve in the second set as the Croat levelled the match.
On the missed opportunity, Rusedski said: "I kind of took my eye off it and played a little too casually and paid the price for it by losing my serve.
"But I managed to put that behind me and then really came out strong for the third set and that was the key."
The first break came in the fourth game as Ancic hit a smash wide and Rusedski clinched the match with another to clinch his place in the next round.