Third placed Cardiff Blues are also in action on Friday night when they travel north to play European Challenge Cup quarter finalists Glasgow Warriors, and the Welsh region will be looking to keep up the pressure on the two Irish sides at the top with a fourth successive win over the Warriors.
Also on Friday night the fourth placed Welsh side Newport Gwent Dragons will hope to build on their European form, which has seen them reach the European Challenge Cup quarter-final, when they face basement side Border Reivers at Rodney Parade.
Friday's final game will have fourth placed Edinburgh keen to reverse the trend of just one win in their last six games when Connacht (who are on a losing streak of five) visit Murrayfield.
With the Magners League's third Heineken Cup quarter-finalists Munster having a free weekend the final game sees Ulster looking to protect their top spot when they face the Ospreys at the Liberty Stadium. Ulster have won their last five matches against Welsh opposition in the League but the Ospreys will be looking for revenge after suffering a thumping defeat at Ravenhill earlier in the season.