Martinez has chosen Romelu Lukaku to lead the line this season and the Belgian's impressive goalscoring form has forced Jelavic to settle for a place on the bench.
The Croatian remains part of Martinez's plans, but he admits Jelavic must continue to impress if he wants to regain his striking role.
"His attitude has been a 10 out of 10 and that's why when a player comes on as a sub he makes a big difference and the team benefits," he told the Liverpool Echo.
"It's a real focus to be as good as you can as an individual, but everything
comes down to the team so Niki, Arouna, and everyone who isn't starting needs to do what they can to help the team.
"In a competition of 10 months you need everyone ready, everyone working hard, and whoever is on the pitch benefits from that. Nikica Jelavic has been really important in the way he works.
"I thought he worked really hard in his early performances and they were really good."
Lukaku has already scored five goals for Everton and Martinez believes the strong competition for places is bringing the best out of the summer loan signing from Chelsea.
"When you see a player performing well on the pitch it's down to the player enjoying his football," he said.
"But as well, it's about the level we have in training and the competition we have for places. We have good options at number nine. Romelu Lukaku is starting games but Niki is essential and Arouna Kone is very important.
"That's what you want in the squad, the moment you lose that you're going to be affected by it. He's vital now, playing or not playing, and he'll carry on being vital until the end of the season."