Jelavic has found the net on eight occasions since he joined the Toffees from Rangers in January.
However, Suker has tipped the 26-year-old to be even more clinical in front of goal over the coming months.
"He can do a great job for Everton," Suker told the club's official website. "The confidence of the team improves when you know you have a striker who can score goals. When people realise he can score in the first or the 90th minute, it is a good thing.
"To score 20 goals minimum, that is the point of the main striker. For every chairman, every gaffer, when signing a striker, that is the point.
"He works well on the training ground and he thinks only about football. I think he can score more than 20 goals next season."
Suker spent two seasons in England during his playing career with Arsenal and West Ham United.