Despite spending time on loan with Swiss side Lucerne earlier in the year, 21-year-old Kasami has forced his way into Jol's plans with the winning goal against Sunderland on the opening day of the season.
While on loan in his native land, the playmaker scored in Lucerne's 4-3 victory over Servette on the closing day of the season before returning to his parent club in London.
Following his header from a Damien Duff corner in Fulham's curtain-raiser, Kasami has become a pivotal part of Jol's plans and the manager believes it is testament to his development whilst on loan.
"Kasami was on the fringes," he told the Fulham Chronicle. "He was another one who wanted to play. He played for Lucerne and made big steps.
"He scored his first goals for the Under-21s last week and played for us against Sunderland.
"He's better than he was before; stronger and one of our key players this season."
Kasami's second-half strike against the Black Cats was his first since joining the Cottagers in 2011 but his tally could move a lot quicker after catching the attention of Jol.