Leftwich wouldn't do much more with the receivers Boller has. If you watch the games, I believe all but one game there has been a dropped long range TD pass. There's no Jimmy Smith in Baltimore. Heap is good yes, but offenses are shutting him down because they know he is the only reliable option to throw it to.
Remember, this is a team that took Dilfer to the Super Bowl. Suggs was a better choice because as we all know, defense wins championships.