UFC's Greg Hardy, 'I Hate People Thinking I'm a Cheater'

Greg Hardy is adamant the illegal knee he landed during his fight Saturday night was NOT intentional -- telling TMZ Sports it was a "rookie mistake" and he desperately wants a shot at redemption.

Hardy was disqualified from the Jan. 19 fight against Allen Crowder for throwing a powerful knee to Crowder's head while his opponent's knee was still on the canvas.

"I feel bad," Hardy told us ... "You never want to break the rules."

The ex-NFL star has only been fighting professionally for less than a year and says, "It was a rookie mistake and I'm a rookie."

Hardy says he's still trying to get a grasp on all of the MMA rules -- but wants the public to know his intention was NOT to take out Crowder with a cheap shot.

Now, Hardy says he would love another crack at Crowder -- and hopes to prove he's serious about becoming a top UFC fighter.

The good news for Hardy ... Greg says Dana White spoke with him after the fight and was incredibly supportive, even though Greg was in a "bad place" mentally.