However, the side will have to be on their mettle against a Gogledd side who were competitive against the Ospreys last week before going down 37-12 in Colwyn Bay.
Neither Griffin or Thomas are in the Blues' starting line-up although the former is named on a strong looking bench.
The game kicks off at 1pm with the under 16s match between Blues South and Gogledd Cymru kicking off at 12.30 at Rumney RFC.
Gogledd under 16 team manager Bryden Lloyd said; "We were delighted to have picked up our first win of the season against the North, but going away to a South side who have lost their opening two games of the season will be a much tougher prospect.
"Having said that, the confidence is obviously good within the squad and the players are looking forward to it."
For the South, it represents an early chance to strike back after successive defeats against the Ospreys, 31-7, and the Scarlets 32-21. Victory is also a must for the region with the North and South sides remaining as the only teams without a win in the competition to date.
The Ospreys and Scarlets are the two unbeaten sides with the latter topping the table at present courtesy of successive bonus points against Gogledd Cyrmu and the Blues South. The Dragons are third, Gogledd fourth and the Blues North and South fifth and sixth respectively.
The Blues and Ospreys remain unbeaten in the under 18s, with the Scarlets having won two and lost one, the Dragons having lost their single game against the Scarlets and Gogledd Cymru without a win from their two games.
Blues under 18: R Lovering; M Roberts, C Driscoll, S Campbell, H Robinson; L Williams, L Jones; D Harris, J Elley, W Griff John, C Hill, M Creech, E Jenkins, T Young, O Sheppeard
Replacements: J Williams, T Davies, J Sienawski, L Young, A Meads, J Griffin, H Thomson
Gogledd under 18: J Hughes; L Isaac, O Aled, W Mitchelmore, H Roberts, J Williams, A Schwarz; E Mason, G Morgan, O Hughes, J Simm, T Davies, G Jones, T Parry, O Jones.
Replacements: J Matthews, J Woods, J Evans, M Bevan, C Holme, A Channer-Hughes, I Ellis
Gogledd Cymru under 16: D Jones; M Richards, J Blackmore, M Jones, A Evans; L Barker, A Bagshaw; R Evans, R Kirby, R Evans, M Francis, J Meadows (capt), E Crowe, J Grundy, R Jones.
Replacements: J Williams, D Goss, A Gwyn, L Evans, P Roberts, R Williams