There's almost no way the Rays "lose" on this deal. One year, one million, this is like the least risky signing you can make, and with a player coming off of a solid year it's a no brainer. Of course, Kapler's not going to have a wOBA of .362 again, to expect that is to expect disappointment. Even so, Kapler's a pretty safe bet to make the Rays a profit here.
CHONE says 0.3 runs above average, Marcels says 1.4. Either way, combine that with 2 < x > 5 defense and a typical 4th/platoon outfielders share of at-bats and we're looking at something like this:
3+0-5.5+10 = 7.5 runs or 0.75 WAR
That means Kapler is underpaid by about three million. Considering Rocco can earn roster bonuses totaling 1.75 million if he's magically cured, the Rays are getting better bang for their buck with Kapler, who can save Andrew Friedman from a burning Tropicana Field, rid the world of MySpace angles, and cure the lizard people while still making only one million.
For Gabe Gross, well, this is just some more writing on the wall. Whatever happens with Gross won't tarnish the fact that he was an extremely solid player for the Rays and at an unbelievably low price. Gross' salary will likely come close to Kapler's meaning he's more likely to go, but I would still anticipate the Rays clearing some more payroll in the coming weeks.
As for new Gabe, just keep your shirt on guy, and hopefully our pitching staff won't give you reasons to make catches like this: