I know the popular wisdom is that the trade of andy Van Slyke to Pittsburgh helped us win a pennant in 1987 by giving the Cardinals solidity "up the middle" with Tony Pena.
But looking back at it on paper it looks pretty bad:
Tony never wins another defensive honor with the Cardinals, he hits only .214 (25 points less than Mike Lavalliere did in 86)
Van Slyke goes on to be an offensive and defensive All-Star, as promised
Lavalliere hits .300
Mike Dunne wins the league in W-L% even after being promoted to the Pirates in June
thoughts? on the whole, good trade or bad?