And while outsiders may have been caught off guard by the extent of the 21-year-old's rapid rise, his former club coach in the capital believes Gatland has made a brilliant call in taking Williams Down Under.
"Lloyd has got everything. You're looking at a real big star in the making," said Young, who starred for Wales at the first World Cup in New Zealand and the 1999 tournament in Wales.
"It's no surprise to me that, once he got in the squad, he's stayed in the squad.
"He's got everything you want from a scrum-half in abundance. He kicks well off both feet, he's got a really strong pass and good distribution skills. The rest he's only going to get with experience and the only way you get experience is by playing.
"He's been unfortunate over the past couple of years with injuries and if that hadn't happened we'd have heard from him earlier as he's a guy that's got everything."
Williams will compete with British & Irish Lions star Mike Phillips and Tavis Knoyle of the Scarlets for the No9 shirt in New Zealand as Wales take on South Africa, Samoa, Namibia and Fiji in Pool D.
And while the tournament will be far bigger than anything the Wales U20 and Sevens squad member has experienced before, Young has no doubt that he will rise to the challenge.
"He won't be fazed. He's going to be nervous - the same as everybody else - but he's got all the skills, all the ability and he's mentally tough enough to take anything that's put in front of him.
"If you put Lloyd on the field, he won't let you down."