There is very, very little reason for a contending team, or any other, to be interested in Mientkiewicz as a starting first baseman. Or a platoon first baseman. He might make a decent reserve. Mientkiewicz is entering his age-33 season, the point in a player's career when he is in danger of running rapidly downhill. The problem with Mientkiewicz is that he's already gone downhill. His bat is a known quantity: he has little power, some plate judgment, and no ability to hit for average.
Goldman is right when he says Mientkiewicz is getting older and has little power. So why do I like the signing?
Well, first, Goldman is wrong on his other two points. Mientkiewicz has more than "some" plate judgment. He has drawn 377 walks in his career, when an average player would've drawn 281. That's a walk rate 34% above average. It's slipped in recent years, but for 2004-2006, his walk rate is 21% above average.
Second, saying Mientkiewicz has "no ability to hit for average" is absurd. His career average is .270. Last year he hit .283. Not a world beater, but a far cry from "no ability."
So what can we expect from Eyechart going forward? ZiPS has his 2007 projection as .255/.342/.383. Marcel has him at .260/.336/.402. Let's average them out: .258/.339/.393. Using a simple Runs Created formula, that works out to 77 runs per 650 plate appearances.
Now that's not very good. The average AL 1B hit .280/.352/.467. In the NL, it was .290/.372/.507. Let's say that the average 1B hits .285/.362/.487, or 102 runs/650 PA. Maybe that's unfair to Mientkiewicz, since the NL is the easier league and those stats should be discounted a bit more, but whatever.
Anyway, we can put those numbers on a scale of batting average with this formula: (1.8*OBP + SLG) * .2595. For Mientkiewicz, it's .260. For the average 1B, it's .295. You can look at those numbers the same way you look at batting average, so they're easy to understand.
Baseball Prospectus figures replacement level in a couple different ways. This one works on the batting average scale, this one on the runs scale. These would set the replacement level for first basemen at a .261 average and 75 runs. What was Mientkiewicz again? .260 and 77 runs. In other words, he's the definition of replacement.
So with the bat, Eyechart gives you nothing. What about defense? He's always enjoyed a fantastic defensive reputation. Checking the stats, there are three that I put any real stock into: UZR, The Fielding Bible and The Fans' Scouting Report.
Mitchel Lichtman hasn't made UZR fully public since 2003, as he was working for the St. Louis Cardinals. For 2000-2003, however, Mientkiewicz was fantastic: 17 runs above average, second best in the majors to Todd Helton.
For 2006, the Dial ratings had him as the second best in the AL at +12 runs per 150 games. I don't put much stock in Dial's numbers, but I mention it only because in his midseason update, Lichtman chimed in to note that Mientkiewicz rated a +12 in UZR. So UZR still loves him.
The Fans' Scouting Report is exactly that: fans rate players in various skills based purely on their own observations. Tango Tiger compiles these scouting reports as a sort of "wisdom of the crowd" judgment. In 2003, the fans tabbed Mientkiewicz as the top first baseman in the majors. Tango worked out his ratings to be equal to +23 runs.
For 2004, fans rated him a 73 (out of 100). No idea how that turns into runs, but it's a great number for a first baseman. In 2005, he was a 67. And 2006 a 69, fourth-best among first baseman. So from a scouting perspective, he's still got it.
Lastly, The Fielding Bible. I don't have it with me, but it loves him. He was rated the second-best first baseman (behind Teixeira). What's more, their stats can't take into account saving bad throws, perhaps a first baseman's most important job. Baseball Info Solutions was curious though, so they watched every play from 2005 and recorded every bad throw saved. The result: Mientkiewicz and Albert Pujols rated ridiculously ahead of everyone else.
Put it all together and it is quite reasonable to say Mientkiewicz saves at least ten runs over a full season with his glove. Considering his brilliance with snagging bad throws, quite likely more like fifteen.
What we have, then, is this: his bat is worth 0 runs and his glove is worth 10-15. That makes him worth 1 win, maybe 1.5. That's below average, but not terrible. By TangoTiger's salary research, Mientkiewicz is worth between $4 million and $6 million.
The X factor is his back. How does his defense hold up following the surgery? It's a fair question, and entirely possible one that will hurt the Yankees. But consider this: he'll make $1.5 million in 2007. Even assuming his true value is on the low-end ($4 million) then the Yankees are paying ~38 cents on the dollar. That seems a more than reasonable gamble to take. And if a better option comes along later, it's an eminently movable contract.
There really is no downside here. Nice move, Cashman.