Knuckles had little intention of striking Crobat if it could be avoided. He saw the beam of light eminate from it and did the instinctive thing - he started to dig.

Knuckles could move through the earth with great efficiency and speed. Some had commented he moved through the earth like a fish moved through water, and while he wouldn't exactly agree with that entirely, it was a close approximation.

He almost literally dissapeared from the field of view and in doing so, he dodged the attack.