Belgium knocked out Brazil in the previous round but were unable to reach their first final after going down to Samuel Umtiti’s second-half header in St Petersburg.
Martinez, though, could not fault the commitment of his men despite the disappointment of missing out on Sunday’s showpiece, with a third-place play-off up next instead.
“Unfortunately for us the difference is a dead-ball situation, a set-play, the game was very close, very tight,” said the Spaniard. “It was going to be decided in one moment, in one touch in the box, a bit of luck in front of goal.
“Attitude and effort was magnificent, we couldn’t ask more. It’s understandable that in football one team loses and one wins but we lost in the right way, giving everything to the last second and pushing for everything to get back into the game.
“[The goal was the] type of detail that can matter in a semi-final in a World Cup. We need to get rid of the disappointment and make sure we finish on a real high. They don’t deserve to leave on a bad taste.
“Disappointment – it is the only thing that matters to go to the final but the players showed an incredible focus and togetherness. The result has to be disappointing but we look forward to the next game and try to finish the tournament on a real high, the players don’t deserve anything else.”
The Red Devils will face the losers of Wednesday’s second semi-final between Croatia and England, having beaten the latter en route to topping Group G.