Yankees Update

Farnsworth For Pudge

The Yankees traded for I-Rod, sending Farnsworth in exchange. The outlook on an emotional level is it's a win-win-win.
Win 1. Subtracting Farnsworth and the attendant frustrations of Farnsworthness.
Win 2. Upgrading Catcher from a Molina-Moeller tandem to a I-Rod-Molina tandem.
Win 3. If the Yankees should contend against the Tigers for the Wild Card or even in the play offs, it's nice knowing their bullpen features Kyle Farnsworth.

Other than that here are some quantitative observations using Fangraphs.
Kyle Farnsworth is pitching reasonably well this year.
There are two features to his success this year, he's not letting them hit homers off him, and he has a high LOB%. Otherwise he's striking out a few more guys than league average, and walking about league average. This all translates into an ERA+ of about 113.
Looking roughly at the difference with League average, we're talking about 0.50 runs per 27 outs over average, unadjusted. If he makes 30 appearance of 1 inning each until the end of the season, we're talking about 3.3 x 0.50= 1.65runs saved above average. Hardly anything to write home about.
More importantly there are other pitchers in the Yankee system ready to step up to deliver that kind of pitching.

Ivan Rodriguez is having an all right year by his lofty standards followed by some years of less-than-stellar production.
He's been slightly lucky with BABIP, and even allowing for that, his RC/27 is bang on average. So as a hitter, he's kind of just on average with a OPS+ of 101. The big clue here as to why this exchange of average players is big is because of this graph:

The Yankees were getting way below average production from their Catcher position. With Jorge Posada out for the rest of the season, the Yankees have been gutting it out with Jose Molina and Chad Moeller, which has been detrimental to the run-scoring end of the game.
Thus, even if Pudge reverts to last year's level of production he's better than either one of them this year. That 2-run difference between Pudge and Molina in say, 150 games translates to about 30 runs, which is 3 wins better. So with about 1/3rd of the season left, the Yankees are now looking at a 1 win upgrade on what they had with Molina.