Posted by Bill Baer on Monday, January 4, 2010 at 10:41 pm

Free agent third baseman Adrian Beltre has finally found a new home. After spending the last five seasons in spacious Safeco Field in Seattle, Beltre is now looking forward to smacking doubles off of the Green Monster in Boston. The Red Sox have signed him to a one-year deal worth $9 million with a player option for a second year worth $5 million.

Beltre has dealt with some minor health issues, but has logged 449 or more plate appearances in every season since he started playing regularly. Outside of his fluke 2004 season, Beltre has been a slightly above average player offensively, with a wRC+ between 87 and 113 in his five years with the Mariners and a career average 107. 2009 was his worst season as a starter, the second straight season in which his OPS declined (100 points from ‘08 to ‘09) and saw his walk rate cut in half from 8% to 4%.

Everyone is well aware that Beltre isn’t known primarily for his bat, however. This is a fact that both fans of traditional fielding metrics and Sabermetrics agree upon. The two-time Gold Glove winner (in ‘07 and ‘08) has a career average UZR/150 of 14 and has been 15.6 or higher in three out of the past four seasons.

According to FanGraphs, Beltre’s glove accounted for more than half of his value last year. Since 2002, Beltre has averaged 4.2 WAR and been worth $14.5 million in free agent dollars on average. Despite his horrid 2009, he was still worth 2.4 WAR, which translates to nearly $11 million in FA bucks.

Clearly, the Red Sox are going to get exactly what they paid for assuming relative good health for Beltre. The move from the vast Safeco Field to the short left field at Fenway Park will help boost his offense a bit, and Kevin Youkilis can take his glove over to first base where he has a career 6.5 UZR/150.

As the title states, the Red Sox can thank the Philadelphia Phillies for their nifty signing. Early on in the off-season, the Phillies snapped up free agent Placido Polanco, signing him to a three-year, $18 million deal to play third base. Beltre didn’t draw much interest after that, as the Oakland Athletics were the only other team to even feign interest.

Due to the Phillies quickly signing Polanco to a below-market deal (and Seattle’s signing of Chone Figgins coming shortly thereafter), the price tag on Beltre was effectively lowered and his leverage in negotiations was significantly weakened. Beltre and his agent couldn’t threaten to sign elsewhere for more money, which allowed the Sox to wait the market out in this game of chicken.

Ultimately, both the Red Sox and Beltre win with this short-term deal, believe it or not. The Red Sox, of course, sign a productive player on the right side of 30 with low financial risk. The short-term deal works for Beltre because he will play in a more hitter-friendly environment with a very competitive, highly marketable team for a season or two, which will help in negotiations in a potentially more lucrative market after the 2010 or ‘11 season. Sure, Beltre would have preferred a three- or four-year deal but that simply was not going to happen with the economics in its current state.

The Red Sox make an upgrade in the infield at both infield corners with one signing and Beltre makes an investment in himself for 2010 and potentially ‘11. For that, they can both thank the Phillies.