The pitcher everyone seems to want this winter is also the pitcher everyone seems to have questions about. What of the medical history? Burnett's averaged just 122 innings pitched per season for his career, and he's already undergone Tommy-John Surgery - does he have an elevated risk of re-injury? And what about that funky groundball rate thing he's got going on? What did he change in 2005 to give him far and away the highest GB/FB ratio of his career?
We've already gone as far as the numbers are ever going to take us in attempting to answer those questions, so now it's time to find out if the pictures have anything to add.
On with it, then:
(-Washington Post)
Burnett's jersey is flying forward, showing just how much force he generates during delivery (you can see the high effort in his face). His head is in good position, eyes seemingly locked in on the target, and he's got his glove directly above his forward knee. His throwing elbow is locked in with his hip rotation, although it looks like he's already square to home plate prior to release. Changeup?
(-CNNSI)
This is a little more troublesome - AJ's square to the plate way ahead of release, he's leaning a little bit to the gloveside, his stride is short (which will force his shoulder up, inhibiting forward motion), and his lead foot is pointing about 15 degrees to the left of the catcher. As anyone who's ever pitched can tell you, command is a function of keeping your body in line towards home plate, so if the first part of you that touches down is off (the lead foot), chances are the rest of your body is going to be off, too. Hello, ball four. And on top of that, trying to throw forward when your body is pointing to an angle will only generate extra stress on the shoulder.
(-MLB.com)
His jersey's billowing, his necklace is flying all over the place, and he's got a facial expression like someone is trying to tear off his nipple rings. In other words, there's a ton of force in Burnett's delivery just prior to release. The problem? Look at his arm - it's almost perfectly straight, which puts a lot of stress on sensitive areas (read: elbow, shoulder). So, what we know is that 1) AJ's delivery builds up to a high-effort, violent release, and 2) his arm is in suboptimal position just when his body is exerting maximal force (letting go of the ball).
AJ Burnett does not have smooth mechanics. He slowly and rather deliberately builds up to a point at which he whips his throwing arm around at almost a Randy Johnson-esque angle. His frequent control problems, per usual, are due to an inconsistent release point brought on by inconsistencies earlier in the delivery, although he's been able to overcome occasional wildness and be a very successful pitcher to date. The bigger concern is that his mechanics aren't doing his future health and well-being any favors. I don't have any images from 2001/2002, so I can't tell you if he's changed anything from his pre-TJS days, but I'd probably put him around a 6 or 7 on a 1-10 scale of injury probability (where 1 is Livan Hernandez and 10 is Ryan Anderson), which is something to consider in contract negotiations.
Understand that this is a risk that exists for every pitcher in the Majors - it's an inherently unnatural motion, and if your body exceeds (roughly) 80 Newton-meters of torque at any point during delivery, you've got a reasonable chance of having something snap. There's no such thing as a predictable pitcher, because anyone could blow out his arm at any given time, even if he's got picture-perfect mechanics. So what you have to do is start weighing the odds, putting everything you know about a guy into a mixing bowl and concluding, based on the available evidence, that he either is or isn't worth the risk. AJ Burnett's mechanics give him a relatively high probability of getting hurt, compared to the rest of the league. He also issues a bunch of free passes. However, he was still able to put together a remarkably healthy, remarkably effective 2005 campaign.
How much does that mean going forward? Do his recent health and performance negate the total bomb potential, here? Does your opinion change as you begin to talk about signing him to a five- or six-year deal?
I don't have all the answers. As a naturally conservative person, I tend to shy away from high-risk/high-reward situations like this one, but then, there's a certain appeal in the "if you're going to get burned, do it on a grand scale" line of thinking that led Bavasi towards Richie Sexson a year ago. So let me just put it this way: I'm not going to complain if the Mariners enter next spring with a Burnett/Hernandez 1-2 punch, but I'll certainly be a little nervous.
Since I kind of went on longer than I anticipated, let's just take a quick look at a fuzzy photographic comparison of 2004 (left) and 2005 (right) AJ Burnett:
The only real difference I can see that could lead to a higher groundball rate is that 2005 Burnett seems to be coming a little more over-the-top upon release - he's still more sidearm than he is overhand, but by bringing his arm up a little bit, it allows Burnett to get vertical motion on his pitches. He's already got a ton of natural movement (seriously, it's almost like watching Juan Cruz), so when you start talking about those pitches breaking at a downward angle, rather than side-to-side, you're going to get bats making contact with the upper half of the ball, drilling it into the ground.
I could be wrong. It's possible that Burnett added to his repertoire or changed some grips bewteen seasons, but mechanically-speaking, that's all I can find.