Hazard is expected to be out for three months after undergoing surgery on his fractured right ankle on Monday.
Speaking after a 2-1 win over the Czechs on Monday, Martinez said he was stunned by Hazard's setback.
"I am very disappointed with Eden's injury. We all know he is a great player, but not everybody sees he is a great human being and leader for us as well," he said.
"He was working hard to be ready for these two games and then this happens.
"There was nobody near him when it happened. He wanted to move from his left foot to his right foot as he lined up a shot and then it happened.
Everything went well with my ankle operation, now I start the road to recovery! I will be stronger. Thank you for your support!! pic.twitter.com/aokirnytkW— Eden hazard (@hazardeden10) June 5, 2017
"We were all in shock and immediately realised it was serious.
"He is already back in London and we have been in touch after the game. He watched the match and congratulated us with the win."
A 52nd-minute header from Marouane Fellaini led Belgium to their friendly win, and they visit Estonia on Friday.