I don't know if this makes me a screamer or not, but I think that the similar stats between Brady and Cassell at this point in the season is more an indictment of Cassel than a cause for hope. There are just so many reasons why Cassel should be able to put up significantly better numbers with this team than Brady could in '01.
The disparity in surrounding talent has already been commented on, but it really can't be said enough. This is pretty much the same offense as the '07 team, which IMO was the best ever assembled. The '01 offense had a porous line, an entirely mediocre stable or RBs, and Troy Brown as the only receiving option above replacement-level.
I also think people are greatly underestimating the amount of inflation we've seen in passing stats in the interceding years. Between the adjustment of rules to favor passing offense, the increasing use of high-percentage passes where teams used to rush, and various other tactical developments, what constitutes "good" numbers has changed. Brady's 86.1 passer rating in 2001 was good enough to rank him 6th in the league. In '07 (so we're comparing full seasons to full seasons) the same passer rating would have him ranked 15th. The 63.9 completion % that Brady had in '01 was good for 4th overall. In '07, it would have been 12th.
So basically, if you look at the numbers, but adjust for league averages and talent disparity, Cassell's performance is pretty underwhelming. Nevertheless, I am an inherently optimistic fan, and I've rationalized a few reasons for hope:
Brady entered the season far more under the radar and with much less pressure on him. The Pats entered '01 with low expectations, and lowered them even more after Drew went down. Furthermore, a large portion of the fans and media didn't even know that the skinny kid from Michigan had beaten out Huard for the backup spot to begin with.
Of even more significance, in my mind, is the fact that Brady was only a year removed from being a frequent starter on his college team. While the extra time in the system means Cassel should know the offense better, combined with his backup status at USC, it's been 9 years since he faced real game speed and pressure -- and even then, it was just high school ball. My hope is that the hesitancy, poor footwork under pressure, and slow decision-making is still a result of a whole lot of rust on Cassel, and that the game will start to slow down on him at some point later in the season.
And remember -- it often happens kind of suddenly for a QB. You can usually pinpoint a span of two or three games where a developing quarterback suddenly "gets it." So while the signs might not be that promising now, and may not change anytime soon, I'm going to keep up hope. I guess that's really all we can do.