Williams has not featured for Cardiff Blues since suffering an ankle injury in the pre-season victory over Bristol Rugby.
However, the talented young No.9 is now ready for his return as the Cardiff Blues Premiership Select look to record a first win of the season in Pool 4 as they face Cornish Pirates twice in a week.
Fly half James Thomas is named in the starting line-up as the coaching team led by Richard Hodges make seven changes to the side that narrowly lost out away to London Welsh.
The other changes in the back line are a call-up for centre Tom Isaacs and wing Richard Smith.
Bradley Thyer and Dillon Lewis are named in the front row and will pack down alongside Scott Andrews who operates at hooker.
The final change is Pontypridd’s Rhys Shellard playing at openside flanker with captain Jevon Groves moving across the back row to blindside.
Coach Richard Hodges said: “There have been a lot of positives to take from our opening pool matches with Nottingham Rugby and London Welsh.
“However, ultimately we have not closed out either game and must take our chances against the Cornish Pirates to record a first win.
“We have a young squad in the British & Irish Cup this season and there is no doubt they will benefit from the experience and exposure. But now we reach the defining period of our qualification hopes with a double-header with Cornish Pirates.”
Cardiff Blues Premiership Select: 15 Aled Summerhill, 14 Richard Smith, 13 Tom Isaacs, 12 Will Rees-Hole, 11 Owen Lane, 10 James Thomas, 9 Tomos Williams; 1 Brad Thyer, 2 Scott Andrews, 3 Dillon Lewis, 4 Miles Normandale, 5 Chris Dicomidis , 6 Jevon Groves (c), 7 Rhys Shellard ,8 James Sheekey
Replacements: 16 Ashleigh James, 17 Joe Jones, 18 Nick White, 19 Jordan Viggers, 20 Lewis Jones, 21 Callum Hall, 22 Harry Davies
