The Chicago Cubs upgraded their infield in a pair of moves Tuesday. They dumped Starlin Castro's once-promising contract on the Yankees and signed longtime super-sub Ben Zobrist to a four-year deal to play second base. It's a stunning fall from grace for Castro and a huge commitment to a 34-year-old hitter who is already showing signs of decline. It makes the Cubs better, but I'm not sure it's "better" enough to justify the money spent.