The young left-sided star was still only 15 when the six foot four Senegal midfielder Diop left the Swiss club for Lens in France in January 2002.
After a successful spell at Lens including a superb World Cup for Senegal in 2002, he arrived in the Barclays Premiership at Fulham last summer.
He's made quite an impact in his first season - grabbing six goals including spectacular efforts against Chelsea and Manchester United.
Indeed, those six goals have come in his last 18 games and, perhaps not surprisingly, Opta statistics show that only Peter Crouch (four) has scored more headed goals than Diop (three) in the league.
Reto, who only turned 19 last month, "I trained with him at Grasshoppers because at that time I was young and not yet in the first team.
"He's very big and strong and I had not seen a player like him before, he's also good technically, some big guys aren't as good but he's a good player.
"He's not easy to play against because he protects the ball so well.
"He's an important player for Fulham now. He tackles and will shoot from far away and has scored some good goals so we must be careful and not let him have a chance, he has a strong shot and a precise shot.
"He always tries to shoot. A lot of players don't try all the time, he does and sometimes it goes into the crowd but sometimes it works. We have to be careful."
Reto Ziegler admits his eyes opened wide the first time Papa Bouba Diop turned up for training at Grasshoppers Zurich.