This is not a Rex-bashing post. It is simply stating the facts: Rex Grossman severly limits what this offense can do.
We have always know Grossman to be a little loose with his though process on Sunday afternoons, frequently being critized by coaches, teamates, and the media, for making bone-headed plays at the worst possible times in games. The criticism is certainly warranted based on his past performances, and we saw it again against Dallas on Monday Night Football.
But, this is more about what Grossman simply is not capable of doing, rather that what he has done, or not done.
The Shanahan offense is based on a lot of play-action fakes, bootlegs, and crossing routes. Kyle Shanahan will often call the same play out of 4 different formations, with 3 different motions, using 3 different receivers. The offense is designed to create mismatches vs. certain defenses.
The offense is also designed to stretch the field, and take some shots against a single high safety look that the offense often generates with the called formations.
There are some obvious problems with Rex Grossman in this type of offense. First, he is lacking the arm strength to get the deep ball over 40 yards. We have seen him underthrow wide open receivers down the sidelines. The Fred Davis play against Arizona down the left sideline is a great example. Fred ended up making the catch, but if Rex could have led him downfield, it could have been a touchdown. Is it a coincidence that we have seen very few deep shots this season? I think not, because combine the fact that Rex has a weak arm on the deep throw, with the fact he likes to step back in the pocket, instead of stepping up, makes for a difficult throw. I don't know his exact measurements, but from what I've seen so far this season, I don't think he can push the ball over 45 yards in the air. We have some speed at the wide receiver position, with Armstrong, Moss and Austin all having the ability to get vertical, but we don't have a QB that can get them the ball.
Another weakness that Grossman has is a lack of zip on the deep out. This is a staple of every NFL football team, and is one of the toughest throws to make in the NFL, but most would think that if the coaches call this play, their QB should be able to effectively execute. This is not the case with Grossman. Again, I see two problems. First, he is shorter than average, and steps back instead of stepping up. Second, he just doesn't have the arm to get the ball on a rope to the outside. The result of this is a ball that floates, instead of zips. As you can imagine, the results are usually not pretty.
Finally, Rex is a very limited athlete(it doesn't help that he added 50 lbs to his 6' foot frame this offseason). He shows no pocket mobility, and is very poor at getting outside on the play-action bootleg. Even if he can crawl outside the tackle box on a bootleg to the right, by the time the WR clears the CB and S, he's too far out of Rex's reach. I will also include fumbles and batted balls in this catagory, as pocket presence has a lot to do with this. You certainly can't expect your O-Line to hold blocks for 5 seconds, and that how long it usually takes Grossman to execute a play action fake. Add another 3 seconds for him to attempt to get outside the pocket, and another second for him to set and thrown, and you have nearly 10 sconds wrapped up in that play. Let me tell you folks, thats not going to work.
Now, Grossman has been good at taking what the defense is giving him so far this season, but it is clear that when it's time to step up and make a play that requires some athleticism and/or skill, he is severly lacking. For us to get over the hump, we need a QB who doesn not limit our offense. I understand that Rex is a stop-gap quarterback for us, and maybe my expectations of him are too high, but I saw glimpses of what this offense can look like, and it pains me to say, we are not able to fully see this, due to the limitations of our current signal caller.