Shanklin appeared as a substitute against Ireland in the second half at Lansdowne Road on Sunday and ran in two tries to give Welsh fans reason to cheer despite their convincing 36-15 defeat.
And Williams believes his Cardiff Blues team-mate could now be given his chance at the Stade de France after it was revealed centre Sonny Parker is out for eight weeks with the fractured thumb he suffered against Ireland.
"Tom showed all the hunger and desire to make a huge impact on the game. He has been frustrated at not starting, just as anyone would be, but he really took his chance well. It was great to have him out there," said Williams.