Jelavic hit the ground running after joining the Toffees from Rangers in January 2012, netting 11 goals in his first 16 appearances, but failed to replicate that form in his first full season at the club, scoring just eight times in 43 games.
|66/1||Nikica Jelavic is 66/1 with Paddy Power to be the Premier League's top scorer
"Niki is a goalscorer. When you see him scoring goals again it’s because he’s enjoying his football," Martinez told The Liverpool Echo.
"He’s been working really hard and physically he still has a little bit to get to 90 minutes. But it’s great to see Nikica coming back with that focus and desire to score goals and be himself.
"When you can score goals in the manner he has done he is going to be an incredible asset for us."
The ex-Wigan boss also revealed his delight at the number of attacking options at his disposal after adding Arouna Kone and highly-rated Barcelona youngster Gerard Deulofeu.
"When you look at the competition for places we have in the forwards and it’s a real strength for the team," he added. "It can only be a good thing to have this strength in depth."