Rovers were edged out in a feisty encounter at the Keepmoat, with Chris Maguire notching the solitary goal just after the break.
There was a hint of fortune about the strike, first when Lynden Gooch got a fortunate touch before his effort came back off a post and straight into the path of a Sunderland player who teed up Maguire for a simple tap-in.
For Doncaster boss McCann, he saw enough from the performance to believe that his side are capable of sustaining their promotion tilt this season.
The result sees Sunderland move up to third but Rovers are still healthily placed in seventh.
"The difference was that they took a chance and we didn't," admitted McCann.
"That's the difference sometimes in a tight game with two teams trying to get out of this league.
"It was a flukey touch from Gooch. He hit it off both feet which I don't think he meant.
"We were then slow to react once the ball hit the post.
"My honest assessment was that they got the goal at the right time but then we matched each other for the remainder of the game.
"We must have hit ten shots over the crossbar which is really frustrating."
Rovers will look to get back on track this weekend when they travel to Coventry on Saturday.