I think that they envision Mookie, Freeman, Muncy, Smith to continue to decline and they want to do something like late 90s yankees or maybe even 2007 sox where you have guys who were the stars for one championship aging, and you want to keep the party going, but you need someone who packs a real punch because your former elites have aged past the point of being able to be your main contributors (on an A++ team) and you want them to be more complimentary pieces.
Or said another way:
They might have wanted to bring in someone who they perceived to be good enough to make up for Mookie, Freeman, Munch, SMith aging to keep it going , and they may have considered Abreu/DUran not that but Tucker that.
You dont bump Muncy,Smith,Freeman down the order for Abreu/Duran but maybe you do for Tucker.