Jason Bay's career numbers are outstanding - .280 AVG, .376 OBP, .896 OPS, and .384 wOBA. Yet his 2007 season looks lousy, to the tune of a .247 AVG, .327 OBP, .746 OPS, and .326 wOBA. Although Bay rebounded over the last two years, should we be concerned that his 2010 might look like his 2007? In a word - no. Bay's line drive rate and BABIP indicate that his awful 2007 season was the product of horrible luck more than anything else.
In 2007, Bay's BABIP was .298, a big drop from his career BABIP of .332. His line drive rate, however, was 16.5% - close to his career rate of 18.3% and actually an increase from his rate of 15.6% in 2006. Since his line drive rate remained consistent, it's reasonable to conclude that Bay hit a lot of balls directly at fielders in 2007, which resulted in his poor numbers. (His walk rate dropped a little too - 9.9% as compared with his career mark of 12.9%, but a normal BABIP would have made his season look a lot better even with the lower walk rate.)
Then when Bay's numbers returned to normal in 2008 and 2009, his line drive rates remained consistent, at 16.5% and 17.7%. We can attribute his increased production then, to the end of his lousy luck, as his BABIPs (BAsBIP?) shot up to .328 and .318, respectively.
So bottom line, there's no reason to be concerned that Jason Bay's 2010 season will look anything like his 2007. Those numbers occurred because of awful luck and are unlikely to re-appear again any time soon.