I think, because he hasn't played in a year and a half, people forget just how talented Sam Bradford really is. Those Rams teams he played for were really bad but Bradford played well for a guy in his mid-20's running for his life. Shit, he's still only 27 years old right now.
Both ACL injuries were "contact" injuries, I'd be more worried if he was running in the open field and pulled up. The American Journal of Sports Medicine conducted a study of ACL injuries and they concluded that ACL injuries don't shorten careers and a large majority are able to continue on their development path. However, they found a common theme to knee injuries that will derail a career: a meniscus tear. Guys like Adrian Peterson did not tear their meniscus along with the ACL, RGIII did tear his meniscus when he tore his ACL. As far as I know Bradford hasn't torn his meniscus. Yeah, the health is a risk but probably not as great as many people think. For a team so shitty in their QB evaluations as the Browns are, yeah, I would've used #19 to get Bradford.
FWIW, I don't see how Mariota fits Chip's NFL offense. Accuracy is #1 QB priority in that system....