Jans worked with the Morocco winger at SC Heerenveen.
"When Oussama first played at Heerenveen he had three different managers in one year and the last of those didn't give him a real chance," he told LFC Magazine.
"But as soon as I became coach I knew he could be a good footballer.
"He's very good in one-against-one situations when he's attacking defenders. He turns them left and right and when he was full of confidence he was a really special player, scoring goals and making a lot of assists.
"He had a really good season in 2010-11 and last year there was lots of interest in him.
"He had some great moments such as the game against FC Twente. Sometimes in your life you play a perfect game. Oussama scored a hat-trick and gave three assists and we won 6-2 against one of the best teams in Holland."