And it's not as if there's not plenty of film on the guy.
This is a QB starved league; if Gabbert was any good he'd have had a starting gig somewhere. Gabbert is getting a start only because Stanton stunk it up. And the only reason Stanton was starting is because Palmer is injured. Arians can babble all he wants about how great Gabbert is......Martz did exactly the same thing about back-up quality QBs that played for him. Arians knows that Gabbert is his last option so the only choice is to build up the guy. But in addition, because the Oline is poor, at least Gabbert can run; he's not a statue. He's not really elusive in the pocket; but he has good athletic ability and speed for a QB so you do have to have lane integrity when rushing him or he'll take off. But he's not slippery like Wilson so that he can extend plays forever.
The last thing the Rams D needs to fret over is Blaine Gabbert. They just need to get reasonable pressure on him, and double that game wrecker Fitzgerald, and the rest will take care of itself. They don't even have to worry about check-downs when AP is in the game because he is a terrible Receiver as a RB.
The Rams have already game-planned for the Cards once this year and it worked quite well. And that with a FAR better QB. Gabbert doesn't really change the equation. The Rams have plenty of front 7 speed to keep Gabbert corralled without having to mush rush. The game plan is: stop the rush and make the Cards one dimensional to end any play pass looks that are legitimate. Keep pressure on Gabbert, hog-tie Fitzgerald, and that'll be that. AP can't win games for you anymore.