BBC Sport - Martyn Williams & Jonathan Davies preview Cardiff Blues v Ospreys
Blues v Ospreys: The pundits' view
- From the section Wales
More than 60,000 fans will watch the four Welsh rugby regions play at the Principality Stadium in Cardiff on Judgement Day IV.
Sport Wales sent Martyn Williams and Jonathan Davies to look ahead to both games.
Here they consider the first match: Cardiff Blues against the Ospreys.