The Croatian struggled for form in front of goal last year and ended the campaign with just eight goals in all competitions.
However, having found the net three times during his last two pre-season friendly outings, Naismith believes that the former Rangers frontman has rediscovered his confidence.
"Throughout pre-season he has looked sharp and he has got a bit of confidence back. I think last season he lost a bit of that through not playing every week," the Scot told the club's official website.
"In training he has looked very sharp as well and maybe the signings that came in have put a bit of pressure on him and he wants to be starting for Everton."
Jelavic signed on at Goodison Park in January 2012.