The American, who has spent almost a decade at Goodison Park, has come in for criticism from some fans for his recent performances, in particular the two goals he conceded against Arsenal last weekend.
Joel Robles played in Tuesday's Capital One Cup victory over Norwich and piled more pressure on Howard with an impressive display.
But Martinez quickly dismissed any suggestion Howard might lose his place for Sunday's Premier League clash with Sunderland and he believes the 36-year-old provides necessary balance to the team.
The Toffees boss said: "Football is about competition for places and that's why it's so great to see someone like Joel enjoying his football, performing in the manner that he did on Tuesday, having an incredible influence, and that's what you want all over the park
There is no difference with goalkeepers
"I'm delighted with the form of Joel Robles and delighted to have the experience of Tim Howard when it's most needed, especially when you've got young or inexperienced players in front of him
"You need that little bit of know-how and direction, and that's why Tim Howard has always been so important, through good moments of form and bad moments of form
His role on the pitch is more important than his individual performance."
Everton have not kept a clean sheet for more than a month and will be without captain Phil Jagielka until Christmas because of a knee injury.
Full-back Seamus Coleman is also likely to miss Sunday's match because of a stomach bug while the other stalwart of their backline, Leighton Baines, is only just returning to training after two ankle operations and six months on the sidelines.
Everton are looking for their first league win in a month after a tough run of fixtures against Liverpool, Manchester United and Arsenal that yielded just one point.
On paper, Sunderland should represent a good chance to get back to winning ways but the Black Cats travel to Goodison fresh from a first win of the season in the derby against Newcastle.
It was Sam Allardyce's second game in charge, and Martinez expects Sunderland only to get stronger under the guidance of one of the Premier League's most experienced managers.
The Spaniard said: "We all know they had a very good reaction to the new manager
Obviously winning the derby against Newcastle has given them that boost and they look like a team with a lot of confidence; they've been galvanised.
"The biggest strength of an experienced manager is that connection with the players
It's going to take a little bit of time but it's clear the organisation, the fight, the desire of this team in the last two games has been impressive.
"And then the way they took their chances against Newcastle was of a real confident side
We expect a really tough team and a team that's going to get better and better the longer that the manager and players work together.
"Looking at our own situation, we want to get the feeling that we had on Tuesday night and carry that on into the league
"It's been a really demanding start of the season but we're very much looking forward to the next nine games and making sure we are as good as we can be and try to replicate the already good signs we've showed
"We're desperate to get back to winning ways and enjoying our football."
Source : PA
Source: PA