The A's added the free-agent right hander for three years at roughly $7 million per. Some questioning the move have done so because they don't think Esteban is worth the money. Fear that a 33 y/o pitcher will be injured or see a drop off in production is understandable, but that doesn't seem to be the issue for the most part. Many don't believe that at his current performance level that Loaiza is worth $7M/year. Using Nate Silver's calculations, Loaiza's 5.1 WARP1 this past season is worth roughly $7.5M and his established performance level of 5.3 WARP1 is worth just over $8.0M.
I don't think it's unreasonable to expect a pitcher entering his mid-thirties to basically maintain his established performance level and if the A's are getting Loaiza's EPL for three years at $7.0M per, it's a slight bargain.
The deal makes sense in a vacuum, at least.
Others are against the deal because they fear that the arrival of Loaiza signals the imminent departure of Barry Zito. First of all, there is no way of knowing if that's true. Second, the stats don't suggest a great loss of production from Zito to Loaiza if it is.
Third, if Beane does decide to deal Zito, it would seem that the Loaiza signing will allow him to get more in such a deal. The A's will be dealing from a position of greater strength and with Loaiza no longer available, the free agent crop of pitchers is weaker. Perhaps I'm being dense, but I really don't understand why A's fan is upset.