I would think most open players see top with side component all the time. After all, almost every topspin shot not hit from chest high would have to have some sidespin added to the topspin. Shell shocked, more likely, like that Canadian open player hitting with Nalbandian.
But overall, a sidespin component changes the way the ball goes thru the air, compared to topspin or flat. The ball slides deeper than expected, and upon bounce, can skidd slightly, then deadball thru the air dropping sooner than it should.
Just gotta play against JimmyConnors to know.