After cleanly beating an offensive tackle, a defensive end or outside linebacker comes tearing around the corner to close in on the quarterback.
Or a running back or tight end will miss a block, allowing a blitzing inside linebacker or safety a clear path to the pocket.
Maybe a receiver runs the wrong route and the quarterback has nowhere to throw. Maybe the quarterback holds the ball too long while trying to find an opening in the coverage.
In every case, the result usually is the same, with the quarterback on the ground and a defender on top of him.
NFL teams constantly deal with these nightmare scenarios.
"That's why offensive coaches lose sleep at night," Detroit Lions offensive coordinator Scott Linehan said.
For them, the never-ending challenge is to find the right balance between the best way to keep the quarterback upright -- and minimize his chances of suffering an injury -- while trying not to compromise the ability to make a big play in the passing game.
In recent years, coaches have tried attacking protection concerns with a variety of strategies. They have used shotgun, two-back and spread formations. Even the trendy "Wildcat" package, made famous in the NFL by the Miami Dolphins last season, helped take pressure off the quarterback because he was replaced behind center with someone else (usually a running back).
"For us, it's always been one of our top priorities," Baltimore Ravens offensive coordinator Cam Cameron said. "We're going to protect the quarterback, but there are certain teams (against which) we'll be exposing him more than we would others, depending on how well teams rush the passer or what type of blitz packages they have. You can say you're going to protect the guy, but if they're rushing only three people and you've got everybody protecting, you're not going to have anywhere to go with the football.
"It's truly a chess match of when you're going to expose him to getting hit and when you aren't."
The burden of pass protection doesn't entirely rest on the offensive linemen. Sure, teams make heavy investments on blockers -- usually tackles -- with high draft picks and multi-million-dollar contracts, but others are just as responsible for protecting the quarterback.
For instance, the Ravens allowed 33 sacks last season. However, according to Cameron, about half of those resulted from "breakdowns by non-offensive linemen." In some cases, running backs and tight ends missed blocks. Other times, the quarterback didn't get rid the ball fast enough. On occasion, receivers didn't get open as quickly as they should.
"I think most sacks, truth be known, come from tight end and running back breakdowns," Cameron said. "And then the third (reason) is the offensive linemen. (Protecting the passer is) what those guys do, that's what they're best at. And defenses do a good job of scheming where non-offensive linemen have to protect the quarterback, and I think that's where you're seeing a lot of your sacks.
"Also, because of changes in the rules, it's more important than ever for receivers to get separation (as quickly as possible). In the old days, it was more about the line because you could truly hit the quarterback. Nowadays, if the receivers are getting separation, the ball's going to come out and then you can't hit the quarterback. If the ball's gone, in theory you can't hit him. And if the ball's gone and you're hitting him, you can't drive him into the turf."
Among the other ways to help keep a quarterback well protected are:
» Heavily investing in the offensive line. This is becoming a clear trend, with 14 offensive linemen selected in the first round of the last two drafts. "The money you spend on the quarterback and what you're asking him to do for your team, you'd better find somebody to protect his blind side, whether that's left or right, depending on whether he's a lefty or right-handed quarterback," Houston Texans coach Gary Kubiak said. "There's no substitute when you draft a kid who plays left tackle for you for 10 or 12 years. That's like finding a quarterback."
» Having strong communication between the quarterback and his center. "I think the most important thing is for a quarterback and center to be on the same page and to understand where the declaration (of the place from where a blitz will come) is, where the stress points are, the protections, what side is hot and what side is covered up," Green Bay Packers quarterback Aaron Rodgers said. "In the protection game, it's all about communication between yourself and the guys up front."
» Adjusting strategy in accordance with the line's development. Said Packers coach Mike McCarthy: "My first year (as coach) in Green Bay, we were very, very young up front. I had more seven-man protection than I had ever run in one season. But I was going to protect Brett Favre, and he was productive with the three-man routes. And we grew with the line. The second year, we were able to balance it out (between seven- and five-man protections). Then we went to a bunch of empty (formations) and had some success early in the year because I don't think people expected it, and Brett handled it very well."
» Having reliable outlet receivers to whom the quarterback can make a quick underneath throw. "So many times in Arizona, we were in five-man protection where the ball had to come out and there had to be an outlet for it at all times," said Kansas City Chiefs coach Todd Haley, the former offensive coordinator for the Cardinals. "But I think that it's harder and harder to find tight ends in the draft each year because when Penn State, Ohio State and Michigan are running spread offenses, it's a pretty strong trend. And where those were once the programs where you were getting your big fullbacks and tight ends, you can't find them anymore. It runs in cycles, but the spread, I think, is here for a little while."
» Running the ball. Of course, the very best way to reduce pressure on the quarterback is to have him do more handing off than throwing. Not only does a solid rushing attack help soften a defense, it takes an opponent out of an aggressive pass-rushing mode by keeping the offense out of third-and-long situations. "A lot of it has to do with what you do on first and second down," Linehan said. "And if you have a good running game and you stick to it and you stay hard-nosed with it, I think, in the end, it's going to be the key to having good pass protection."