To still be able to stop the run, mostly. If we didn't sign Brockers, I'm assuming we would have made every effort to retain Pierce. If we did neither, how confident would you be that teams couldn't do to us what we do them, which is run for 150-200 yards a game on them?
You think a front 7 of Brandon Williams, Calais Campbell, and a group of largely backup linebackers like Fort, Bynes, etc. is going to stop any team that's effective in running the ball?
Heck, I'm looking just at our division. Browns bring in Stefanski, who loves to run the ball, and have a very formidable backfield in Chubb and Hunt. The last thing they're going to want to do is give Mayfield 600+ pass attempts.
The Steelers have an old QB, with a very limited receiving core, with major elbow problems. They don't even know if he'll be ready to play yet. You think their game plan is the 2018 version of Ben, who had 675 pass attempts?
And then you have the Bengals, who will be starting a rookie QB. You think their plan is 600+ pass attempts for a rookie in a division that fields three pretty good secondaries?
If I'm playing the Ravens, even now with Brockers, my game plan would be simple... pound, pound, pound. Its not going to be to test the secondary.