"Everyone was focusing on trying to score and we didn't control Villa's threat. Without Tim today it would have been a very difficult second half," Martinez told reporters after the game as he praised both Howard and Osman.
"I'm really pleased. I said before that we have a really strong squad. All that matters is every player is ready to help whenever they are called upon.
"I told Leon that it was going to be a good opportunity for him in the last 20 minutes with Villa tiring and when he came on it was a masterclass of getting on the ball in the attacking third."
Everton are now fourth in the Premier League thanks to their win this afternoon.