Marouane Fellaini (Supplied)
The 30-year-old scored a crucial goal for Belgium in their 3-2 comeback victory against Japan in the last 16 of the World Cup in Russia on Monday, and could make the Red Devils' starting XI against Brazil in the quarter-finals on Friday.
"I think he is player that you have to work with to appreciate what he really brings," Martinez told Goal.com website.
"He (Fellaini) gets underestimated in his technical ability. I think he is a footballer that has got a level of technical control and ball control a lot higher than people think."
Fellaini recently signed a new two-year contract at Manchester United and Martinez believes he is a player with whom every manager would love to work.
"He was born to compete," continued Martinez. "He is a winner. I think he finds football as a good opportunity to show how life should be. His interpretation of life is the way he runs the football game.
"As a team player he always sees that every action is the end of the world and that makes him a warrior and someone that every coach and manager would love to have in his team."