No,I think the point of his not being in the derby was why should he spend the whole break in NYC just to participate in it?The rest of the participants were in town for the game anyway-not so for Giambi.
As far as his being ABLE to perform in the derby,I don't think that would of been a problem.As Aaron said earlier,he can still launch one when he gets ahold of one..and could he really have done any worse than Piazza did in past derbies,or even Mauer in this year's??

Take care,
Joe