The pair moved across London from Craven Cottage to Tottenham in the final days of the summer transfer window and, though the Dutch coach admitted his disappointement with the Belgian's departure in particular, he hopes that Dimitar Berbatov can provide a boost this season.
Jol told the Daily Mirror: "A couple of months ago I read somewhere in the papers that Dembele said, 'Maybe I owe it to the manager to stay for another year?' so I was fine and didn't anticipate anything.
|80/1||Dimitar Berbatov is 80/1 with PaddyPower to score a hat-trick in Wigan v Fulham
"Then he left three days before the transfer window closed, so that is why we got Dimitar. I don't think Dimitar will leave us in the next six months.
"Dembele was my best player on the ball and Dempsey was my top scorer.
"We had to come up with something and we did it against West Brom thanks to Berbatov and we did it two weeks before with Mladen [Petric]. I am very happy that we have that sort of quality up front."
Jol also revealed his intention to help improve Fulham's weak away record this campaign with a trip to Wigan on Saturday.
"It's been the same for the last 10 years that we couldn’t win more than two or three games away," the former Ajax and Spurs boss said.
"So to get four last year was probably our maximum and that is what we have to improve on. If we get five or six that would mean we will finish in the top seven or eight.
"But for us it's different now – we have to build again and take two steps back to go forward again.
"Hopefully we can do that because of the likes of Petric and Berbatov but we also need players in midfield to contribute goals. You have to score at least 50 goals to do well in this league."