A pitcher is credited with a save when that pitcher finishes a game won by his team, was not the winning pitcher and one of the following:
1)Pitches three or more innings
2)Comes into a game with a lead of three or less and pitches at least one full inning.
3)Comes into the game with the potential tying run on base, at bat, or on deck
In other words, a save will only be given for a three run lead if the pitcher pitches an entire inning. Cordero came in with one out, bases empty, and a three run lead. The potential tying run was not on base, at bat, or on deck - hence no save.