His family wanting to go home to California after 2 seasons certainly wasn't factored into the original position. While uprooting his family and moving them here to TO had to be a big part of the 3 year contract otherwise it wouldn't have been worth leaving SJ.
Truth be told Marleau is being a real classy guy here, by allowing the Leafs with a full NMC to deal him to Carolina as that is no closer to his family than Toronto is, and he is making a personal sacrifice that is not in his best interest, but for the sake of the Leafs benefit.
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Its that type of character that likely was a main reason in bringing him to Toronto in the first place to mentor the younger players and help in their development. Matthews and Marner certainly hold him in high esteem and consider themselves part of his extended family.