If you are the Mariners they would say its a good deal. Having signed him to a long term deal they are expecting a .900 OPS(Maybe .280 .540 .360). Since he would be in Seattle that .900 OPS would translate to around .950. Helton comes in at 1.070 consistantly. Depress that to .980 for Colorado effect.

They are close to the same age. Plus a number 1 rookie in a 20 team league will score a very good prospect. Plus Silva(know real thoughts on him).

While the trade seems fair, I personally wouldn't trade Helton for two reasons. The main reason being I like lefties, and for a lesser reason I don't think the game adjusts up or down for park effects as dramatically as it should, maybe 60% of the effect(guestimation).