I disagree dreadlockera the most important aspect of a QB is and always was physical abilities. The problem is that most of the time to even get a starting gig a QB must have physical skills that are often comparable to each other and then from THERE the ones who separate themselves are the guys with the intangibles. But you almost never take a guy without the physicals and all the intangibles, and make him into a great QB. The most often used example is Montana, but if you talk to a few guys who do evaluations, they all say Montana had a very nice accurate deep ball.
Tom Brady has a good arm too and a very nice deep ball that has broken open plenty of games, especially when it seems like the game is on the line. Remember our first game against the Patriots? In OT, after two missed FGs that could have won the game sapped our spirits, Tom Brady launches like a 69 yard pass to win the game.
Jake Delhomme, aside from having a great TEAM surrounding him, also has a very nice arm as well....but the way that team is able to play he probably doesn't even need that I mean it seems like the worst his stats are the better the team does.
I'm not saying you need a rocket. But you need a nice deep ball, you need a pretty good arm, and most every starter in the NFL has that pretty good arm. Jay Fiedler and Brian Griese might have the weakest arms among starters in the NFL right now, truth be told. What I'M trying to figure out personally from the reports is whether Rivers has that arm that is pretty strong, good enough. I think what it sounds like is he can get pretty good zip on short passes but his long throws are nearly hopeless. This makes him maybe a little better then Fiedler IF he turns out to be able to read defenses as well as Fiedler.