Two gold gloves, and his 127 OPS+ his rookie season was the worst of his career. There's no way that's not an A. Adrian Beltre career OPS+, 114.
If we accept that realistically Miggy is more of a 1st baseman than a 3rd baseman, the only 3B I'd take over Longoria is David Wright, and even that is very, very close.
On top of everything else, Longoria is only 28. Wright and Cabrera are 30, Beltre is 34.