If I read the rules correctly, a Knight (and only a Knight) can get the
ball off the side or out of the corners.
+---+---+---+
|(O)|-N-| |
+---+---+---+
| | | |
+---+---+---+
| | * | |
+---+---+---+
The Knight kicks the ball (marked O) to the square marked by the
asterisk.