The average American League designated hitter had a wOBA of .341, or generated 1.38 runs per 600 plate appearances. The Rays DH collection of Cliff Floyd, Eric Hinske, Jonny Gomes, and others combined for a DH wOBA of .338, or about two less runs per 600 PA than the average DH. Jason Giambi has had wOBAs of .418, .350, and .379 the past three seasons. In fact, Giambi's wOBA low since joining the Yankees was .339. So even at his worst, Giambi has been better than the Rays DHs.
Ideally the Rays could add a hitter with defensive value, but sometimes exceptions can be made. Giambi could provide a two-win upgrade simply from his hitting. If you assume he falls off a half of a win each season from here on out, he's still a 2 WAR player next season, and a 1.5 WAR player in 2010, that's worth roughly 18.46 million dollars, or 9.23 million per season. Let's hope a combination of an oversaturated market and having friends like Carlos Pena on the team, plus the possibility of a World Series ring, weigh heavily in Giambi's mind when it comes time to sign.