Mechanics. You hear scouts and evaluators rave and rant about them throughout the NFL draft process and again if and when players struggle in the NFL.
While it's possible to overcome mechanics—there is a select few who have found a way to excel despite less-than-stellar mechanics—most are severely limited by the lack of ideal delivery or footwork.
Here's a look at two quarterbacks playing well in spite of mechanical issues and two who need major work in the offseason if they expect to remain starters for long.
The issue: throwing motion.
When Philip Rivers was entering the 2004 NFL draft, there was no doubting his production, ability to win or toughness. Instead, scouts questioned his unorthodox sidearm delivery.
Rivers' NFL coaches wisely didn't try to adjust a throwing motion that was successful at the college level. That doesn't mean Rivers' motion is anything other than ugly.
Rivers' motion is unlike anyone else's in the NFL. Where most quarterbacks execute an over-the-top delivery, Rivers' shoulder is at an odd angle. His elbow is out wide, as opposed to in near his side like most top quarterbacks. In fact, the way Rivers contorts his elbow to shoulder looks painful.
Compare Rivers' motion to Tom Brady's (shown above). We see that the ball is much closer to Brady's helmet, which puts less stress on the shoulder and elbow. Also, note that Brady's arm is straight up and down, while Rivers' bends out away from his body at the elbow. Does that look comfortable to you?
Rivers has been a successful NFL quarterback in spite of this, but it does bring into question how long his arm can hold up due to the abnormal stress he's placing on his joints.
The issue: hanging in the pocket, throwing off back foot.
When healthy, Matthew Stafford has been one hell of a quarterback, playing productive football and showing the toughness and accuracy to be a leader and winner at the position. That said, there's one area where Stafford can really clean up his act.
Stafford has a tendency to throw off his back foot, which hinders the mechanics and balance of his throws. This is an issue for many young quarterbacks who aren't quite used to the punishment of an NFL defender crushing their bodies.
It's tough to blame Stafford; he's playing behind one of the worst offensive lines in the NFL. But he can cut down on his interceptions dramatically if he can be more willing to either step up in the pocket or stand in and deliver the ball without fading away from the line of scrimmage.
Because of his arm strength—and Stafford is by far one of the strongest passers in the NFL—he's able to compensate and throw without bringing his feet through the throw with him. This is a bad habit that Stafford needs to correct.
The issue: balance and vision.
Blaine Gabbert's biggest issue since coming into the NFL has been his tendency to either fade back away from the pocket or escape the pocket too soon. Granted, he's not had much of an interior offensive line at times, but Gabbert's been labeled as gun shy in the pocket.
There are few things a quarterback can do that are as bad as throwing off balance. From Pee Wee football up to the NFL, quarterbacks are trained to have a balanced, consistent drop step.
Gabbert's footwork in the above image is a clear indicator of a mechanical problem that he has not overcome. This isn't a still from his rookie season—that's NFL Week 9, 2012, against Detroit.
While Matthew Stafford can compensate for his habit of fading back in the pocket while throwing, Gabbert isn't strong enough to do this. The Jaguars don't ask Gabbert to throw downfield often, but even shorter throws are negatively impacted by poor footwork in the pocket.
Another major issue for Gabbert is that he doesn't seem to understand when to throw the ball away.
Take this play as an example: The defensive end hurdles the left tackle, leaving Gabbert in a one-on-one situation with the defensive end. In college, a quarterback can win this battle, but it's unlikely to happen in the NFL. Gabbert has two options—run through the clear opening or throw it away. He chooses neither.
Gabbert has open field to run through if he wants to pick up yards, but he hesitates. That indecision leads to a sack.
The issue: arm-thrower.
Mark Sanchez was a highly-touted prospect coming out of USC, but after two years of game managing his way to AFC championships, Sanchez is being asked to carry the New York Jets. A major reason for his struggles can be found in the way Sanchez delivers the ball.
We want quarterbacks to be balanced when they throw and balanced when they finish throwing. You'll see this called "follow-through" or a "transition."
When I was coaching quarterbacks, we'd spend most of our time in passing camp working on taking a balanced drop step—be it three, five or seven steps—and then learning how to throw on balance so the hips and feet carry over through the throw. Sanchez is regressing in this regard.
Sanchez is capable of throwing with good lower-body mechanics. The image above is what we want to see from No. 6 when throwing. Just like in Little League baseball when learning to throw to first base, step into the throw.
The good news about mechanical flaws is that they can be corrected, and in some cases—like Rivers and Stafford—quarterbacks can overcome their flaws on their way to being highly productive franchise quarterbacks.
For Sanchez and Gabbert, the arm talent is there; they just have to clean up their footwork and decision-making.