Thursday’s pairing of the Los Angeles Angels and free agent slugger Josh Hamilton is a curious match.  As I discussed yesterday, the Angels already had an abundance of outfielders, two aging sluggers earning in excess of $20M each year (Albert Pujols and Vernon Wells) and a greater need for pitching than offense (team finished 4th in 2012 runs scored while finishing 7th in team. There are early rumblings that Hamilton’s signing was precipitated by ownership and forced upon the club’s baseball operations department. Owner Arte Moreno wants to win – and be top dog in town (over cross-town rival Los Angeles Dodgers).

So how smart a signing was it? What kind of performance can the Angels and fantasy owners expect from Hamilton in 2013?
Hamilton’s signing proves a compelling piece of analysis; there are fewer change factors involved than in most other major free agent signings; he’s not changing leagues or divisions, he’ll face many of the same pitchers as he has for the past five years with the Rangers.  And yet, he’s exhibited a diminishing skillset over the past three seasons (his O-swing % has increased each year since 2009) and is leaving one of the best hitter ballparks (Arlington Stadium) for one of baseball’s pitching-friendly parks.  While unexplainable performance spikes and valleys occur, we can examine Hamilton’s change in parks and forecast their effect over his 81 home games in Anaheim.

First, I’ve pulled the park effects of the two stadiums for 2012.  I’ve specifically focused on the park effects for left-handed batters in both (as Hamilton bats left-handed). Keep in mind that 100 represents a neutral playing effect for the batter, with each point above 100 representing one percent above the MLB park average:

Keep in mind that these numbers represent totals over 81 games, not 162, so the park effects reflect the true hitting environment a player faces in his home stadium for a full 162 game season (the second 81 games being on the road). As Hamilton is not switching divisions, he’ll experience the same ratio of his games in stadiums outside the AL West and thus we can appropriately analyze his performance change through these park factors alone.

Looking back at his 2012 performance, Hamilton sported the following fantasy line in 636 at bats:

.285 BA, 84 1B, 34 2B, 2 3B, 43 HR, 128 RBI

While RBI is a valuable component of fantasy baseball, we can’t consider it in the analysis as it is highly dependent on the batters/runners hitting in front of Hamilton. 

Once we factor the park differences as stated above, we can forecast Hamilton to produce the following 2013 fantasy line over a steady 636 ABs:

.231 BA, 81 1B, 31 2B, 1 3B, 37 HR

What we see is roughly a 5% decrease in performance across the meaningful fantasy baseball categories.  Further, when we consider hitter aging curves, batters typically reach their peak power performance (in fantasy, measured through 2B, 3B, HR) at age 29, Hamilton is already a declining asset in the fantasy world.  Power hitters’ performance typically declines 1-2% in their age 31 and 32 season, so there’s further reasonable downside to Hamilton’s projected 2013 numbers.

The short of it, Hamilton should not be considered in the first-round of the fantasy draft, and The Angels will not gain the offensive performance that we saw from Hamilton during his Ranger' days. 

This might get ugly as he approaches his year-37 season.