Bottom of ninth inning. Visiting team ahead 2 - 0, with their closer in the game. Visiting team has retired the first two batters. The 3rd batter of the inning doubles. The batter now up is the DH who is 0 - 3 so far in the game. The on deck batter is also a power hitter, but with a lesser BA. What would you do in this situation??
This isn't strangers in the night. In pro ball it isn't even about what happened earlier in the game. The pros have a significant amount of detail on hitter vs. pitcher that assists them in their decisions.
Barry Bonds got an IW with the bases loaded because the odds were in favor of it minimizing how many runs would score in the inning (his walk plus what would happen next).
While my answer is correct at most levels, like Rich stated at the MLB level they have extensive historical data on every matchup in every situation. Now the manager gets past baseball logic and looks at historical facts.