If the Raptors' situation is truly a problem--there are worse things, after all, then playing near-.500 basketball, especially against a schedule that has been one of the league's 10 hardest in the early going--I'm not sure it is one that is easily fixed. The natural tendency is to believe that the route to success for an imbalanced team is to improve the weakness while maintaining the strength. Sometimes that works, as it did for the Mavericks under Avery Johnson, but it can also backfire as it did on the Suns a year ago.
In this case, it seems especially clear that the same things holding back Toronto's defense are responsible for the success of the offense. The Raptors have all the tools for success scoring the basketball, boasting shooters at virtually every position (the worst in the starting lineup might actually be the shooting guard, rookie DeMar DeRozan), a post-up threat in Chris Bosh, good passers in point guard Jose Calderon and small forward Hedo Turkoglu and the ability to run one of the league's most dangerous pick-and-rolls with either Calderon and Turkoglu on the ball, Bosh rolling and Andrea Bargnani spacing the floor.
Taking out the weak defenders in the starting lineup, especially Calderon and the poor-rebounding Bargnani, would mean sacrificing on offense. The trade-off doesn't seem to make sense for Toronto. Plus-minus numbers offer some confirmation for this notion. Though the starting five has struggled on defense, 82games.com indicates it has outscored opponents by about seven points per 100 possessions. Only one reserve in the Raptors' rotation has a substantially positive net plus-minus--guard Marco Belinelli, who is not exactly a defensive stopper.
Inevitably, coach Jay Triano must take some of the blame for a defense this weak no matter how bad the personnel. Still, the offense has exceeded expectations entering this season, which points in Triano's favor. While SCHOENE accurately predicted Toronto to be 29th in the league in Defensive Rating, the Raptors' offense was projected to be about average. Part of this discrepancy can be explained by the impact of Turkoglu's passing and Bargnani's shooting, which have helped their teammates, but no one anticipated Toronto to be one of the best offensive teams in NBA history. So it's not clear that a change on the sidelines would help either.