(Photo Credit: Mark J. Terrill, AP)

Over the course of his storied big league career, Pettitte’s always had the label of a “gamer” but not a staff ace, or in the minds of many, a Hall of Famer. When you think of the best pitchers over the last 10 to 15 years, Pettitte’s name probably doesn’t enter the conversation. And they’d be right — Pettitte has rarely been the best pitcher on his own team, let alone one of the best in the game, which is not to say he hasn’t been a very good pitcher for a long time — he has. That alone deserves some pub. Very few guys throw about 15 seasons of 117 ERA+ baseball.

As we look back and reflect on his starts over the course of his career, we should also be mindful that Andy’s started the majority of his games behind some of the worst defensive teams in the modern era. Though those teams were also great-hitting teams and had the greatest closer of all time (boosting his wins), it probably negatively impacted his ERA. While it’s anyone’s guess if this is his last season or not, if he were to go out, it would have a very Mussina-esque feel to it. Here are the stats this year: 10-2, ERA of 2.82, 105 IP, 90 hits, K/BB of 2.52. His last two seasons were quite different, as I’ll explain.

What has Pettitte done differently to go from a mid-4′s ERA mid-to-back-end starter to a guy on pace for a 20-win season and an ERA under 3? Well, not much, really. And yet, tons. Let’s get the basics out of the way: Andy’s generated a .265 BABip against, a number that’s unlikely to remain; a LOB% of 79.5%, and his FIP is a charming but not great 3.93. In short, Number 46 has had considerably good luck this season. His BABip against is roughly 50 points below his career average, his strand rate is about 8 percentage points lower than usual, and his walks and strikes are typical of Andy seasons.

But beyond just luck, Pettitte has pitched very well. It’s not all smoke and mirrors. In fact, the reinvention of Andrew Eugene Pettitte appears to have happened last year. Pettitte is no longer a guy relying on extreme groundball tendencies. Prior to 2009, Andy was generally eliciting a groundball in 50% of at bats or more. Over the past season and a half, it’s been closer to 43-44%, which may also explain the lower BABip (last year was .301). His WHIP is also down to 1.15, which is certainly aided by the low BABip, is also minimal due to the better walk rate at 2.65.

Pettitte’s fastball is better, he’s walking fewer, he’s working his cutter, getting more swinging strikes and more players getting under the ball, which accounts for the 13.7 infield flyball rate, the highest it’s been since 2004. The fastball, I think, may prove to be the biggest step forward. Though he’s working at a slightly lower velocity, it’s been worth 2.1 runs above average this year, a full 8 runs above last year’s total. The cutter hasn’t been as effective this year at 7.2 runs above average (last year was 11.2), but when mixed with a more lethal curveball he throws more often, it’s likely the pitch used to cause infield fly balls and weak contact. Andy’s closing the half season with batters swinging at more pitches outside the zone and less pitches inside the zone, although they are making more overall contact.

We hear all the time that baseball is about constant adjustments. It seems that Andy fundamentally altered the way he faces batters in the 2009 season and 2010 is the more chiseled version of that pitcher. He went from throwing 52% fastballs in his 2008 season with 27% cutters (calling Phil Hughes!) with a 10% usage of his curveball and 6% on his changeup en route to one of his worst professional seasons (per ERA, at least — his other peripherals were fairly good, better than 2007, even). How much of injury factored in is hard to say, but he has changed his approach, that much we know. He’s now throwing more fastballs (57%), fewer cutters (20%), more curves (13-15%) and mixing in a changeup every now and then (still between 6-9%).

It’s also worth noting that the “gamer” bestowment on Andy is actually true. As much as I hate unsubstantiated narrative, this one appears to be true. In his first three innings, Pettitte’s seen opponents hit .286/.340/.436 against him. Of his 36 runs given up this year, 22 came in innings 1-3, and nine of those in the first frame. But after that? Lights out. He’s holding batters to an OPS of about .560 afterwards. Lefties this year have also hit a comical .158/.196/.208 off the Big Bayou Boy in 2010. He’s always been effective against southpaw hitters, but that’s roughly 300 OPS points better than usual. Seriously, that is not a typo.

Zips predicts Andy to throw a 6-5 record with an ERA of 4.59 and an FIP of 4.24 in 96 innings. I see why they’re bearish on him, it’s unlikely he can continue with such good fortune (though he has sustained a LOB% of near 80% once in his career, his 2005 season in Houston), but there seems to be good reason to believe he can keep the BABip lower than he has historically, and his SO/BB has climbed as the season has progressed, indicating he’s hitting his groove.

Pettitte’s career, like that of his teammates Jeter, Posada and Mo, is that of an outlier. He’s still successful not because he has the good fortune of having amazing stuff, but because he’s able to adjust his approach as hitters have taken advantage of his mistakes and shortcomings. And really, that’s the mark of a great player. He may not be a 200 IP, 200 K, 3.00 ERA pitcher, but there’s good reason to believe if he continues to work on his craft — as I expect him to — he can be the 200 IP, 150 K, 3.80-4.15 ERA pitcher he’s been for the better part of his career.