Marcellus Wiley denies poking his estranged wife's cheek during their alleged altercation ... and now he's claiming he has a witness who will back him up.

The former NFL star filed a motion to modify his bond conditions earlier this week ... in which he says, "The only other witness to the alleged 'cheek poke' did not in fact witness any physical altercation nor touch."

He also mentions in the documents that the current bond conditions prohibiting contact with his minor children will prevent him from providing adequate childcare. He says his estranged wife, Annemarie Wiley, works outside the home four or five days a week and obviously cannot look after the kids during those times.

Marcellus is asking for the judge to modify the order to allow him to continue his work from home as a sports broadcaster and serve as the primary caregiver for the kids when his wife is out of the house.

As we previously reported, Marcellus was arrested and booked on a domestic battery charge on the Fourth of July after Annemarie told cops he poked her cheek and threatened to kill her.

Annemarie filed for divorce shortly after Marcellus' arrest -- and alleged she was previously raped by him. He's denied all the claims she's made against him.