Most pitching projections are based on facts pertaining to the pitcher's past. Do we know whether they consider the advantages or disadvantages of switching to a different home stadium? Different league? Different division? What about defensive changes on the pitcher's team or other news your projection system didn't pick up on? Here is a breakdown of new context we should consider for American League pitchers:

A.L. East

The Yankees and Red Sox have both replaced their leftfielder by adding another centerfielder. New York traded for Curtis Granderson while keeping Brett Gardner - who will presumably play more than Randy Winn. Yes, Johnny Damon is an ex-centerfielder, but he lost a great deal of range last year. He was actually below average for a leftfielder. Of the returning Yankees 38 year old Andy Pettitte could hold back the aging process a bit by having more of his frequent fly balls caught. In the bullpen Alfredo Aceves and Phil Hughes will benefit the most. Mariano Rivera will not be helped at all.

New addition to the Yankees rotation Javier Vazquez will benefit from an all around better defensive team, but, of course, will be hurt more than that by moving to the toughest division in baseball (and that's an understatement). The last time Vazquez played for the Yankees six years ago, it did not go well. After three years in a row of ERAs in the 3.00s and over 200 innings, Vazquez had the worse ERA of his career 4.91 and the fewest innings since he was in the Majors for good.

Boston picked up Mike Cameron and will move Jacob Ellsbury to leftfield previously manned by the much more sluggish Jason Bay. Boston also changed the left side of their infield. Adrian Beltre is a big improvement on old and hobbled Mike Lowell. Marco Scutaro is not quite Alex Gonzalez defensively, but he's better than Julio Lugo or Nick Green. Thus all returning Red Sox pitchers will be helped significantly this year - especially the left-handers: Daisuke Matsuzaka, Jon Lester, and Hideki Okajima.

One left-hander not helped in Boston will bw Brian Shouse who comes from the Green Monsterl-ess Tropicana Field and who already enjoyed an outstanding left side of the field (Crawford, Bartlett, and Longoria).

Boston is John Lackey's first new Major League team. Like New York, Boston can be tough on their players, so how Lackey will adapt is unknown. The Red Sox did not have an efficient defense last year, but this year's improvements could bring them up above average. The one thing we can safely say will hurt Lackey is having to play against New York, Tampa Bay, and a rapidly improving Baltimore on a more regular basis.

I expect no significant change in context for returning Tampa Bay pitchers. New closer Rafael Soriano will be hurt more by his switch to the A. L. East along with the move away from the Braves' Turner Field than the help he will receive from the more efficient fielding Rays.

Toronto's pitchers will likely suffer from their late season moves last year of trading away Alex Rios and Scott Rolen. Both above average defenders will be replaced by decidedly below average defenders (Travis Snider and Edwin Encarnacion, though, the more average of-3b Jose Bautista is strongly a possible regular in either spot. Mid-season call-up Mike Rzepczynski should be affected the least due to his high strikeout rate and the fact that a higher percentage of his innings were pitched without the help of Rios or Rolen.

Brandon Morrow gets additional whammy knocks by arriving from the league's best defense to baseball's worse nightmare of a division - especially since Toronto isn't even one of the power houses in the division. The hope is that Brad Arnsberg and the Blue Jays can tap into Morrow's buried potential and vastly improve him. Those are speculative advantages vs. concrete disadvantages.

Baltimore has new corner infielders both of whom are getting shifted from more demanding positions. Shortstop Miguel Tejada becomes a thirdbaseman and will likely be a nice improvement on last year's Melvin Mora. Garret Atkins switches from thirdbase to firstbase and not likely to be worse than Aubrey Huff who played the most games there for Baltimore last year. Groundball reliever Jim Johnson stands to benefit the most from these changes. Give left-hander Brian Matusz a little boost due to his facing more batters who would be inclined to hit towards third-base. Like the Rays, the Orioles are also importing a closer from the Braves: Mike Gonzalez. As Baltimore's defense was inferior to Atlanta's, just about everything for Gonzalez will be changing for the worse.

Kevin Millwood escapes the hitting paradise of Arlington, Texas only to jump into the fire of the A.L. East. Baltimore did have one of the poorest defences last year, while Millwood was benefiting from rookie wunderkind Elvis Andrus. The net effect should be a downer for Millwood.

A.L. Central:

Having more of Delmon Young and, of course, no Carlos Gomez will be bad for Minnesota's fly ball pitchers, but having J.J. Hardy and Orlando Hudson up the middle of the infield will make their groundball pitchers even happier. The gainers are: Nick Blackburn and Matt Guerrier a little. The losers are: Kevin Slowey, Scott Baker, and Jose Mijares.

Jon Rauch is also a fly ball pitcher and the Twins outfield is below average defensively. Don't nick your projection for him too much. Though, he has moved to the superior league, the A.L. Central is probably inferior to the N.L. West and since Rauch is a reliever, facing pitchers is less of a factor as relievers often face pinch hitters anyway.

Of course, the big question for the Twins is what effect their new stadium will have. The outfield distance is about the same, foul territory is apparently smaller, but the temperature will be much cooler during the cooler months. In other words, it is too soon to suggest an adjustment, though, you might consider buying Twins hurlers now and selling them in June.

The Tigers will likely be starting rookies in the place of Gold Glove winning secondbaseman Placido Polanco and outstanding centerfielder Curtis Granderson. From the reports I've read, it is more likely Scott Sizemore and Austin Jackson will be below average at their position than have the acclaim of the predecessors. Adam Everett's value is all in his ability to play shortstop. At 33, he is reaching his expiration date. Hence, all the returning Tigers' pitchers may be a little disappointing. Phil Coke should be hurt the most as the Yankees had a more efficient defense than the Tigers last year.

As for Max Scherzer, he, too, has left the National League's strongest division for the American League's weakest. Call that a wash. The fact that he is leaving Chase Field (Coors Jr.) for Comerica Park tilts the balance favourably for Scherzer.

Overall, what the White Sox lose by inserting Mark Teahen in their infield instead of Chris Getz, they gain by playing Juan Pierre and more of Alex Rios in place of Jermaine Dye and bits of Brian Anderson and Scott Podsednik. The winners on the south side of Chicago should be fly ball pitchers Daniel Hudson, Bobby Jenks. Meanwhile ground ball pitchers Mark Buehrle, Matt Thornton, Tony Pena, and to some degree Gavin Floyd will be less pleased.

Jake Peavy already made the same divisional switch as Max Scherzer, except the park effect is the opposite. Peavy moved from the easiest park to pitch in to one of the American League's most difficult.

Cleveland will have a new look at three different positions, but it is difficult to determine what impact they will have if any. It is unknown who their starting left-fielder will be. The leading candidate Trevor Crowe will likely be a much better outfielder than Ben Francisco, but all of the other leading candidates would likely be worse: Jordan Brown, Shelly Duncan, Austin Kearns, or Nick Weglarz. Mike LaPorta moves to first-base where he trained in the minors only last year and looked OK in his 10 games there with the Indians. A rookie will do most of the catching, but we don't know if it will be Lou Marson or Carlos Not-the-guitarist Santana. If Crowe does win the left field job, look for a little improvement from David Huff, Chris Perez and Jensen Lewis, but not the others. Catching changes are not often good for the pitchers. The Indians have mostly extreme ground ball pitchers.

Jose Guillen played 69 games in the Kansas City outfield last year and Mark Teahen played 32. The rest of the innings were taken up by David DeJesus and a battery of borderline Major League centerfielder types. Their 2010 outfield will consist of Rich Ankiel in center, DeJesus in right, and a battery of borderline MLB CF types - hopefully without any Jose Guillen content, but he may end up out there occasionally anyway. That constitutes a slight improvement, but not enough to take the trouble of adjusting your Royals pitchers. Much more significant is that they will no longer have Teahen in their infield. He was traded for Chris Getz and Josh Fields. Getz will most likely be a defensive replacement for Alberto Callespo, if he doesn't win the job outright, while Fields will likely back-up a hip surgery recovered Alex Gordon at third and, well, I don't know if anyone has figured out what else to do with Josh Fields. Resultantly, the Royals pitchers should be a better off this year, especially the ones with a decent ground ball percentage such as: Gil Meche, Luke Hochevar, Brian Bannister and to a lesser degree Kyle Davies.

A.L. West:

Chone Figgins was outstanding as the Angels' third-baseman. It is doubtful the Brandon Wood will be nearly as good. However, the rest of the Angels' infield is young enough to improve enough to make up for the Figgins to Wood deficit. On the other hand, their outfield is old enough (Abreu, Hunter, and Rivera) to get significantly worse than last year - enough to affect Jered Weaver, Scott Kazmir, Brian Fuentes, Scott Shields, and to a lesser degree Ervin Santana and Joe Sanders.

Joel Pineiro has to be one of the more difficult pitchers to project. Three years in a row ('04-'06) his ERA increased by nearly a full run to 6.36. Most pitchers wouldn't survive such ugly ERAs, but a shift to the bullpen and to Boston then St. Louis in 2007 brought his ERA back down to the 4.00s. Returning to the rotation in '08 and it was back up to the 5.00s. Then suddenly last year at age 30 it was 3.39 with a career high in innings. As any sabermatician knows, his stats should regress enormously this year. Add that he has shifted from the weakest division in baseball to the second strongest and you can be assured that Pineiro will keep his streak of having the numeral to the left of the decimal of his ERA different from the previous year. Now, factor that he has moved from a pitcher's park to a neutral one. Then consider St. Louis had a more efficient defense than Anaheim's Los Angeles last year and that the Angels will be a little worse next year and you might conclude low strike out Pineoro's ERA may go all the way back to ugly.

Fernando Rodney is a high strike out and ground ball pitcher who was helped more by Detroit's strong infield last year than he will by the Angels' average infield this year. Comerica was once believed to be a pitcher's park, but has been a bit on the hitting friendly side of average the last three years.

Julio Borbon is expected to takeover the Rangers' centerfield from Marlon Byrd. That is probably a good thing, but I'd be cautious about bumping Texas fly ball pitchers Neftali Feliz, Derek Holland, Brandon McCarthy, and Frank Francisco too high. We don't know how good he will be.

The league's best defense, yes: Seattle, just got even better. Jack Wilson, Chone Figgins, Casey Kotchman, and Milton Bradley replace Yuniesky Betancourt, Adrian Beltre, Russell Branyan, and a consortium of leftfielders led by Wladimir Balentien. The entire group of returning Mariners pitchers will learn to like their new team-mates very quickly. The one player they might well miss, however, is Kenji Johjima. Sometimes breaking in a new catcher is bad for a team's ERA. Though, Rob Johnson started almost half of the Mariners' games last year, he is merely place-keeping for Adam Moore, who is hoped to take over Seattle's catching duties any time this year. Temper those anticipated improvements accordingly.

Seattle's superior defense and pitcher friendly home probably does not quite make up for the superiority of the A.L. West over the N.L. East - let alone the fact that the A.L. uses the DH. It will be interesting to see if Cliff Lee can produce three great seasons in a row - especially after pitching as an ace all the way into the World Series.

Brandon League should be very happy to leave the gruelling A.L. East to pitch for a far superior team defensively.

Oakland joins New York, Boston, and Chicago by improving their outfield defense by simply playing a centerfielder in leftfield. Coco Crisp will be taking over center allowing Rajai Davis to replace Matt Holliday in left. They join Boston, Seattle, and arguably Minnesota and Kansas City as completely remodelled left sides of the infield. (Teahan played more games at third last year than Gordon.) Kevin Kouzmanoff should stabilize Oakland's shaky thirdbase situation with better defense and offense than Adam Kennedy and Jack Hannahan. A healthy Eric Chavez is a dream they have not officially given up on. They are giving Cliff Pennington a chance to grow into a shortstop that will be an all around improvement on an old Orlando Cabrera - having officially given up on Bobby Crosby. Firstbase will also improve defensively if  Daric Barton wins the job for the entire season. Jason Giambi played more games there last year and neither Jake Fox nor Chris Carter appear to be an improvement. So, give all returning Athletics pitchers bonus points for an overall improved defense - not to mention points for being on one of the best teams in the league at pitcher development.

Finally, let's look at Ben Sheets. Well, better to let a physiotherapist look at him. I have no idea how good he is going to be. Baseball Prospectus's Will Carroll likened him more to Brad Penny than Chris Carpenter, but I'm not sure if that is because he doesn't think he will fully recover back to his previous level or because his mechanics cause him to break down. Whatever your projection, do take into consideration that like Pineiro, Sheets is moving from the easiest division to the 2^nd toughest. No other context issue matters nearly as much. He will get just a little help from the Oakland Coliseum as Miller Park isn't particularly friendly to hitters either. The improvements in Oakland's defense only take it to what Milwaukee had last year, so he gets no help there. While Oakland excels at getting the best out of their pitchers, they can't brag about keeping them healthy. That is what Sheets needs most.