The Scarlets, who went down 18-6 to the Blues back in September, finished their group games with six win from sevens games. Impressive wins against Gogledd Cymru, home and away, preceded arguably their most complete performance of the season when they beat the Ospreys 22-16 at Llandarcy.
The Blues, who kicked off their campaign in winning fashion against today's opponents, are the only unbeaten side in the competition. Guided by their outstanding outside half Joseff Griffin, they won six matches on the bounce including a 57-0 home win against Gogledd Cymru and a 65-0 success away in North Wales.
On top of notable friendly wins in Ireland and England, the capital region might fancy their chances of recording a seventh successive win at the end of what has been another outstanding season of age grade rugby in Wales.
However, the Scarlets, who have won the toss for the home dressing room, will be keen to follow on from their recent wins against the Dragons and Ospreys.
Players to watch for the Scarlets include Luke Hamilton, Luke Williams, Aled Davies, Curtis Morris and Tomos Ellis Williams, all of whom have crossed the try line this season. For the Blues, key players include Owen Sheppeard, Sam Campbell, Harry Robinson and leading scorer Griffin.