The Belgium international was making his first appearance since injuring an ankle in the Merseyside derby on January 28, and marked the occasion with only his second goal since the end of November.
Even then he was not 100 per cent, but Martinez knew the Chelsea player would make a difference to his side, who had failed to score in three of their last four league matches.
"Romelu is someone we have missed for a long time and it was a clinical touch," he said of Lukaku's 81st-minute strike.
"He had a bit of a chest infection and I knew he would be more effective finishing the game rather than starting.
"West Ham had an accumulation of bodies behind the ball, but the last few minutes become harder to defend with Rom with his freshness and power.
"That injury is exactly what he needed. This is the first season he is starting to play 90 minutes consistently, leading the line, taking responsibility.
"In January he was starting to feel tired. I think we are going to see the best of Romelu until the end of the season, fully refreshed."
Up to the goal, the closest either side had come to scoring was when Steven Pienaar had his shot tipped on to a post by goalkeeper Adrian.
But the main talking point was Gareth Barry's challenge on Kevin Nolan in the first half, when the Hammers captain looked like he would have a clear run into the penalty area which match official Jon Moss saw as fair.
"I don't think there is much in there. There is a bit of contact but Leighton Baines is recovering and I don't think that is an incident the referee can give as a free-kick," said the Toffees boss.
"I think you are looking for those actions too much. I think the referee did the right thing to play on.
"When I watched it live, I didn't feel it was a free-kick."
Hammers boss Sam Allardyce, understandably, felt differently.
"There's no doubt about that in my mind," he said.
"Gareth Barry was at the time, from my position which was behind the referee, there was no obscured view of Gareth Barry pulling Kevin Nolan down. That was a key moment.
"Kevin would have been perhaps scoring another goal because of the goalscoring form he is in; he's scored four in the last five.
"It looks like he (Barry) is stopping a goalscoring opportunity and a red card. I am really disappointed in that but I can't control that."
Allardyce withdrew Carlton Cole on the half hour as he did not think he was getting enough from the striker and replacement Andy Carroll, who dislocated a finger at one point in the game, made a difference.
"We couldn't get out of our half and Andy had to come on to get us out of our half more because Carlton's hold-up play wasn't as good as it normally is. Andy held it up more," said the Hammers boss.
Of Carroll's dislocated finger, Allardyce said: "Andy didn't seem to have much trouble with the physio popping it back in for him.
"It made me wince but it didn't make Andy."