The Yankees have had two mainstays at first base over the last decade: Jason Giambi and Mark Teixeira. Both were free agents that signed long-term deals for more than $100M. Giambi was supposed to bring one of the best bats in the league while Tex was supposed to bring an excellent all-around game.
One discouraging fact is that they both declined in their first three seasons in pinstripes. Giambi - who had an incredible 198 OPS+ in his last season in Oakland (2001) - went down to 90 in 2004. Tex went from a 152 OPS+ in '08 to 117 last year. Is it merely that they were both on the wrong side of 30? Did they get pull happy in Yankee Stadium? Did defenses get wise to their hitting tendencies?
Giambi's OPS+ his first three Yankee years: 147
Tex's OPS+ his first three Yankee years: 128
Giambi only played 80 games in his third year (2004). If he'd been healthy, his WAR would certainly be higher than Tex's, but to his credit, Tex has been and should continue to be healthy. He's made up for his (relative) lack of hitting via health (400 more PA) and defense (20 runs better than Giambi) over the aforementioned time spans. In fact, Tex hasn't played fewer than 145 games in any season of his entire nine-year big league career. Giambi, who we've come to think of as a chronically injured player, had been very healthy before '04, averaging 150 games the previous six seasons. So who's to say Tex won't become injury prone? Giambi appeared to be rolling along, then all of sudden couldn't stay healthy. In hindsight, it seems that PEDs may have played a part, but can we assume Tex is totally clean?
Giambi's bat declined his first three years in the Bronx, just like Tex, but he rebounded big time his fourth year. It would be amazing if Tex could maintain his current batting line (126 OPS+ before last night), which has also declined each of the last three years.
What about Tex's peripherals? So far, he's striking out far less than normal, but also walking less. His Yankee peripherals (groundball, flyball and line drive rates) are all in line with his pre-New York days, but there's a noticeable dip in BABIP. Empirically, it seems that opposing defenses are employing a shift against him (as a left-handed batter) far more than they used to, which could explain the decline in OPS+ while maintaining the same peripherals.*
Tex has been worth $55.3M since joining the Yanks (per FanGraphs), a bit less than what he's been paid ($62.5M). I believe, however, that 2012 will be far closer to '09 and '10 than '11. His BABIP hit a career low last year (despite otherwise normal peripherals); that should regress to normal this season (it has so far). And while Giambi's health continued to decline into the latter part of his contract, Tex should remain healthy and provide value via defense, something Giambi never did.
* Unfortunately, batted-ball peripherals don't go back to Giambi's (original) Oakland days.