The Red Devils legend is set to end a 29-year association with the famous club following the sacking of Louis van Gaal as manager.
Former star winger Giggs, who served as van Gaal's assistant for the past two seasons, will reportedly turn down an offer from incoming manager Jose Mourinho to remain in the role which Wales manager Coleman feels could be the catalyst for the 42-year-old's coaching career to really kick off.
"It will be hard for him to leave but it might also give him that little bit of a spark. It's a new challenge for him, something different and out of his comfort zone," said Giggs' former Wales teammate.
"He's a legend at United. He can be there as long as he likes but if he goes somewhere else he may find that little bit of a spring in his step. He's never been afraid of a challenge, I know that.
"He's a determined character and it could work in his favour coming away from something he's known for so long because you can get a bit stale.
"I'm not saying that he has but it might be a bit of a kickstart for him."