Having been part of the Welsh back row for 100 Tests Williams - who retired last season - knows all about their current strength in depth in the blindside flanker position.
Dan Lydiate is the star performer in the role at present and with former skipper Ryan Jones a more than able deputy Pretorius seemingly has his work cut out.
But, having declared his interest in representing Wales way back in 2010, Williams believes the South African-born blindside specialist could soon be juggling his domestic Blues role with international honours.
"We've got unbelievable back-row strength in Wales. But Andries is more than capable of getting into that squad," said Williams.
"He's one of the most dedicated players I've ever seen, so his standards off the field are as high as his standards on it.
"He's probably on the radar of the Welsh management.
"We know how good he is at the Blues and, hopefully, if he stays injury free this year he'll have another big year."
And Williams believes Pretorius' versatility means he could could also make his Wales bow at No. 8.
Again, as is the case at blindside, Newport Gwent Dragons' Toby Faletau seemingly has the starting berth locked down, however Williams added: "He's an outstanding number eight and he's only going to get better and better.
"But he's also a forceful guy. He's one of the most dedicated players I've ever seen, so his standards off the field are as high as his standards on it.
"He's certainly someone for the younger players to follow."
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