I’ve never been able to track it down, I even asked Joe Haldeman and he didn’t know.
This is what I remember. I read it as a youth so it would be an easy reader. The protagonist is a baseball player. Different planets in the system play each other, but his hand-eye coordination is so good that the different gravities don’t affect him much.
A war starts against creatures that shoot lasers out of their single stalked eye. The pilots on Earth ships are equipped with handguns that shoot out sticky, expanding rubber balls to seal any hole if the ship is punctured by an alien laser.
The protagonist crashes on a planet with an enemy alien and saves the aliens life.
Peace ensues when it is discovered that the aliens ‘laser’ is actually a communication beam and war started over a misunderstanding.