Kasami scored an early contender for goal of the season on Monday night with a sumptuous two-touch volley which sailed over Crystal Palace goalkeeper Julian Speroni from 25 yards.
The Swiss has not enjoyed the easiest of rides at Fulham since joining the west London club on a free transfer from Palermo in 2011.
The 21-year-old has started just nine Barclays Premier League games and last season he was so desperate for first-team football that he took a 50 per cent pay-cut to join Swiss side Lucerne on loan.
The midfielder is out of contract in 18 months and has been linked with a move to Juventus, but Jol says the best place for his development is Fulham.
"He's still not the best player in England, but I think in two or three years he could be a big player," the Fulham boss said.
"Then maybe Juventus can come here and pay a lot of money for him. That would be good for everyone!
"I told him to count his blessings and to be happy at that age playing Premier League football.
"He needs to keep his feet on the ground. He's a very level-headed boy."
Tottenham took little time to tie Townsend down to a long-term contract following his heroic England debut, but Kasami will have to wait longer for a new deal at Fulham.
Jol thinks Kasami, a naturally left-sided attacking midfielder just like Townsend, still has work to do before he deserves new and improved terms.
"There will be a situation in five or six months time that we have to talk and extend his contract," Jol added.
"If he didn't score that goal it would've been a different story.
"He could've gone to other clubs when he left Palermo but he came here.
"He started off well but he had to learn a lot and that's what he did.
"If you take the likes of Kyle Walker, Kyle Naughton and Andros Townsend, they played for other clubs then came back. Now Townsend is the one I go to the stadium for. He's a good player, almost like Arjen Robben, but not as good. He makes things happen for his team and Kasami's the same.
"He's got a very good shot and free-kick, so if he works hard he will be more and more important for us."
Kasami is likely to retain his place in Fulham's starting XI for Saturday evening's match at Southampton.
Captain Brede Hangeland is unlikely to play as he has a nerve problem in his leg while midfielder Bryan Ruiz is a doubt because of a back injury.