Ankle Sprain
We've all rolled an ankle before, but few of us rolled our ankle because a 300-pound endomorphic defensive tackle dropped his enormous ass on it. The bigger difference, however, is that us normal guys go on limping for weeks, while most athletes tape the ankle, tape their shoe, and head out for the next play.
Bell's Take: "We grade ankle injuries 1, 2, or 3. Grade 1 is minor, but would disable us average humans. For athletes it has to be grade 2."

Bruised Ribs
When asked what difficulties arise from a rib injury, Bell responded, "Umm, breathing." So unless you discover another way to oxygenate yourself, you're activity will be limited to tonsil hockey. Yet the Ravens' Willis McGahee and the Eagles' Brian Westbrook are both playing through bad rib injuries at running back, a position that has relied increasingly on breathing in recent years.
Bell's Take: "For most normal people this would be uncomfortable for weeks... Some players just get a pain-killing injection directly in the area, and suit up."

Shoulder Subluxation
This is what happened to Chad Johnson—er, Chad Ocho Cinco—in the preseason. Basically, your arm gets jolted out of place but doesn't fully dislocate, so from that point on, every hit or awkward landing can make it feel like it's slipping in and out of place. As for Ocho, his total of games missed due to the injury has been nada.
Bell's Take: "We wouldn't be able to lift our hands over our head, requiring about 4-6 weeks before we regained normal range of motion and strength. For these guys, it's maybe one or two before they're back in business."

Contusion
It's a fancy word for a bruise, but not the "banged my shin on the coffee table" variety. More like the "took a Cadillac to the sternum" variety. These tend to occur in bigger muscles like thighs, hips, chest, or back. The muscle bleeds and tightens up, and the only real solution is ice, compression, and tears. So throwing 35 passes is not a generally recommended cure.
Bell's Take: "The muscle gets so stiff, you would feel like you couldn't run or push through it at all. But that's exactly what an athlete will do."

AC Sprain
The AC joint is the point where your shoulder blade meets your collarbone. It's also the part of your body that takes the brunt of impact when a giant, speeding lineman drives your body into the ground before falling on top of you. And a sprain just means the ligaments are torn to some degree. Put that all together and you get, well, a pretty damn uncomfortable situation.
Bell's Take: "For us, it would be painful to throw a softball underhanded. [The Steeler's] Ben Roethlisberger has this, and is throwing a football 60 yards downfield."