Martinez snapped up Atletico Madrid's Joel Robles after becoming manager in the summer, having worked with the goalkeeper last season during a loan spell at Wigan Athletic.
However, Howard remained the first-choice option between the posts and has repaid Martinez's faith with a series of accomplished performances.
"Tim has been faultless since the start of the season," said Martinez in the Liverpool Echo.
"It is important in every position that you have good competition for places and have options.
"Joel Robles, who won the FA Cup last season, is going to bring that threat but I thought Tim Howard showed on Saturday just what a magnificent moment of form he is enjoying. And what a magnificent goalkeeper he is.
"I can really say that I've not seen him do anything that has not been of the highest, highest level so I am really pleased in the competition we have in that position."
Martinez has tried to evolve Everton's playing style since taking charge and has been pleased with the way they have responded, even though it was a slow start with three straight draws.
He said: "Looking back now at the start of the season we were very disappointed with the three draws we had.
"The points tally is a very good one, the performances have been very, very good and what I have really been impressed with is the attitude and focus of the players.
"They are a really strong unit who have been successful over the years and for me, it was important to keep that.
"But they have also opened up to doing things in a different way and that has been impressive."
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