The Blues sealed a deal for the Ajax winger on Thursday, with reports claiming the summer move will be worth €40 m.
Cascarino told talkSPORT: "He has got everything.
"He is a great set-piece taker. A bit like Mahrez, he can go at people, he can dribble. He can just go at you and go past you. Fantastic assist record, a hell of a talent and I think Chelsea are very lucky to get him.
Cascarino added: "He's like Mahrez physique wise, he will go past you, he will see passes, he's quite direct, he's just got a great array of set-pieces that he will take and get on the ball.
"He has got everything in the game. He destroyed Real Madrid last year, he really played a big part in them getting the better of Madrid.
"He had a few issues, people questioned a few issues in his personal life but he's obviously overcome them. He has got everything."