Hazard has started just one game for Madrid this season but captained his country in their Nations League matches against Wales and the Netherlands last month.
His limited minutes at club level have sparked debate over his role at the World Cup next month, but Martinez insists the 31-year-old remains a key component of the squad.
"Is Eden Hazard still an important player for the national team? Yes, 100 percent," Martinez told state broadcaster RTBF. "I think his experience, the way he affects the opposition, the way he's still beating players, he's creating a real threat. For me it's a profile that is one of the best in the world in terms of being able to play."