Brees showed little prior to the 2004 season, which is why SD drafted Rivers. It was only during the 2004 season that he showed he could be a top-flight QB (of course having Tomlinson, Gates, and a good O-line helps). His games prior to that were marked with inconsistency and had Rivers come into camp on-time, he likely would have been given the starting nod.
And I can't understand why people still think JP is a question mark? The Bills were in EVERY game this year, and if not for mistakes made ALL-AROUND, the Bills would be undefeated. That's all you can ask of a young QB, especially one with only 8 starts and 2 seasons under his belt (at the start of this season).