In football (and I'm sure many other sports) if you're a goal down, you can push up with more attackers, and put more pressure on the opponent to try and get a goal back. If you're leading by a goal or two, you can keep more men behind the ball and make it more difficult for the other team to score a goal.
In baseball, if you go a few runs down, can you change the way you play and become more offensive than you were before? Do the fielders change position? Does the batter swing at more pitches than he would have done before?