Of all the major sports, baseball has changed the least over the decades. Baseball has more continuity, allowing for comparisons of players from different eras. You can't do this in football. For example, Johnny Unitas' statistics do not compare at all to Peyton Manning's. Heck, Unitas doesn't even compare to Jeff Garcia. Football has changed too much for the statistics to be meaningful between eras.
Baseball had a 70-year period in which player statistics were comparable, from the end of the dead-ball era in the 1920s to the early '90s. The early '90s saw some changes which led to an explosion of offense. More runs, more home runs and higher ERAs became the norm. Twenty-three hitters clubbed 50 or more home runs in seasons between '95 and '07. Before '95 it had been done only 18 times in all of baseball history. Regrettably, today's stats don't compare easily with those of even 20 years ago.
Three factors contributed to the offensive explosion of the modern era:
1. Performance-enhancing drugs -- Drug usage, especially amphetamines, had existed for a long time, but steroids and HGH became widespread in the '90s. Suddenly every power hitter looked like the Hulk.
2. Expansion -- Baseball expanded twice within a five-year span. In '93, franchises were added to Arizona and Colorado, and in '98 to Tampa and Arizona. Expansion added another 48 pitchers to major league rosters. Sluggers such as Ken Griffey Jr. feasted on these "Quadruple A" pitchers that should have been in the minors.
3. Ballparks -- Baseball began a massive stadium rebuilding effort in '92 when Oriole Park at Camden Yards opened. Seventeen ballparks have been built since then. Most replacements were more hitter-friendly than their predecessors. Outfield dimensions tended to be smaller in the new stadiums and foul territory was reduced.
Fortunately, there are no current plans to expand and the impact of drugs is lessening due to tougher testing practices. Ballpark rebuilding continues to be a factor, however.
The building frenzy brought us one new ballpark in '08, Nationals Park. Next season we will see two new stadiums in New York: Citi Field (Mets) and the new Yankee Stadium. The new Yankee Stadium will have the same dimensions, and the huge left-center gap. Citi Field's dimensions will be asymmetrical, unlike Shea Stadium. It will be deeper in right-center than in left-center. It's hard to tell how it will play, though in general it should be more hitter-friendly than Shea, a notorious pitcher's park.
Nationals Park plays fairer than RFK Stadium did. The power alleys in RFK were a pitcher's best friend. Nationals Park is more hitter friendly, though not exactly a hitter's park. It is in the middle (no. 15) in terms of runs scored, with slightly less than average in home runs hit (no. 20 out of 30).
The fantasy owner must take the stadium into account when setting lineups and when evaluating talent. For example, in head-to-head leagues, avoid pitchers starting in hitter-friendly stadiums such as Coors Field (Colorado), Cellular Field (Chicago) or Chase Field (Arizona). Double-down on pitchers starting in Petco Park (San Diego), PNC Park (Pittsburgh), Dodger Stadium and Shea Stadium.
You also need to factor in the home field when your fantasy players are traded. There are a number of well-known players on the trading block. The change of venue could give their stats a boost or drag them down. With that in mind, let's take a look at some players who are, or could be, on the move.
Xavier Nady, OF, Pirates
Nady is having a career year and is on his way to career highs in HR, RBIs and average. Nady (.327, 12 HR, 56 RBIs) is doing this despite playing in pitcher-friendly PNC Park. Nady is hitting .350 on the road versus .304 at home. So a trade to Arizona, for example, would enhance his fantasy value.
Mark Teixeira, 1B, Braves
Teixeira will be a free agent and Atlanta figures to trade him before the deadline. He hits well at Turner Field (.306), but he could end up in Arizona, Baltimore or Anaheim -- all hitter havens.
A.J. Burnett, SP, Blue Jays
At 10-9, Burnett is on his way to a career high in wins, despite the high ERA (4.84) and WHIP (1.45). He strikes batters out, which is gold in any fantasy format. The Yankees are interested,and if he ends up in New York that would be a big plus for fantasy owners. Burnett's lifetime ERA at Yankee Stadium is 3.18 and his WHIP is 1.18. That's much better than his career numbers at Toronto's Rogers Centre (3.94 ERA and 1.28 WHIP).
Matt Holiday, OF, Rockies
Holliday is a .301 hitter on the road, but that's still 57 points below his Coors Field average. That's consistent with his career home/away splits. No surprise that Holliday hits for more power in the thin air of Colorado; 11 of his 16 HR were hit at home. Holliday is a good fantasy player in any city, but he loses a lot if he leaves Colorado, especially if he ends up in Tampa Bay or with the Dodgers.
Jason Bay, OF, Pirates
Bay is a better hitter at home (.302) than on the road (.269), which is surprising. PNC Park is definitely a pitcher's park. If the right-handed Bay is dealt to the Yankees, his value decreases.
Greg Maddux, SP, Padres
Maddux has a no-trade clause, but he might wave it to go to a contender. He is only 3-8, but he has pitched much better than that for the weak-hitting Padres. Maddux is a good fantasy pitcher at home in Petco Park. Away from Petco, Maddux is just plain bad. His ERA at Petco is 2.51, but on the road it's 6.27. A trade to the Brewers or Cubs would be disastrous to his fantasy value.
Randy Wolf, SP, Astros
The just-traded Wolf is owned in slightly more than a quarter of leagues, but that should drop with his deal to Houston. Before the trade from San Diego, Wolf's home/away splits were like Maddux's: 5-4, 3.17 ERA at Petco, versus 1-6 with a 6.63 ERA on the road. The short porch in Houston (315 feet down the left field line) will not help. This Wolf is a dog.
Joe Blanton, SP, Phillies
Blanton was having a terrible season in Oakland before his trade to Philadelphia. He leaves Oakland's McAffee Coliseum, a great pitcher's park, with its expansive foul territory. Enter Philadelphia's Citizens Bank Park, a veritable launching pad. It's not a good match for a guy that pitches to a lot of contact. Blanton's ERA was more than a run lower at Oakland (4.63) than on the road (5.74). In Philadelphia it should be well north of five.