Found this pretty interesting. From Tom Verducci at SI.com:
I wrote back in January about how [Mark] Teixeira, coming off a .256 season, is so mechanically unsound that he is going to continue to decline. Teixeira collapses on his back side and swings up on the ball. I wrote then, "The style means Teixeira must catch the ball out in front of him and leaves him prone to lifting the ball rather than driving through it. As he ages, Teixeira becomes an even more extreme fly ball hitter and pull hitter, trends that mean he will continue to lose points off his batting average." [...]
His batting average on balls in play has dropped every year with the Yankees: .302, .268, .239. That's not unlucky. It's symptomatic of his hitting style. His fly ball rate has increased every year as a Yankee (37 in 2008, followed by 44, 46, 47). His infield pop-ups, which are no different than strikeouts, and were as low as 14 in 2008, have grown to 21, 30 and 27 as a Yankee.
Teixeira's swing simply is not built to make him a consistent clutch hitter. After coming to the Yankees with a .308 average with runners in scoring position in 2008, he hasn't come close to that kind of reliability with New York (.264, .273, .268) -- especially in the postseason environment.
Teixeira turns 32 years old next season. The Yankees already have age-related issues with Alex Rodriguez and Derek Jeter. You can put Teixeira in that category, not because of health, but because his pull-happy, fly ball swing is the kind that doesn't age well, sort of like those of J.D. Drew and Adam Dunn.
According to Cot's Baseball Contracts, Teixeira is under contract until 2016 and is making $22.5 million annually. A-Rod is signed through 2017 and will make $29 million next year alone. Jeter is signed through 2013, averaging $16.5 a year, and has a 2014 player option. Something to think about as we lust after Prince Fielder or Albert Pujols.