Williams made his senior rugby debut for Cardiff at centre against Bedford in February 1999. He again played in that position for the club against Ebbw Vale two years ago. He scored tries in Cardiff victories on both occasions.
In the pack, Robert Sidoli joins Craig Quinnell in the second row and Nathan Thomas has recovered from injury and starts at number 6.
Team: Craig Morgan; Jonny Vaughton, Rhys Williams, Tom Shanklin, Fereti Tuilagi; Lee Thomas, Dean Dewdney; Gethin Jenkins, Gareth Williams, Martin Jones, Craig Quinnell, Robert Sidoli, Nathan Thomas, Kort Schubert, Martyn Williams (captain)
Replacements: Andrew Lewis, Rhys Thomas, Deiniol Jones, Nathan Budgett, Richard Smith, Nick Macleod, Shaun James
Referee: David Changleng (Scotland)