Exeter Chiefs will face the Heineken Cup champions for the second successive season after they were drawn with Toulon.
Castres booked their place in the Top 14 semi-finals after a 22-12 victory over Montpellier at Stade Pierre-Antoine.
A losing bonus point for Montpellier in Bayonne was enough to eliminate Perpignan from the race for the play-offs.
Second takes on third in the pick of the Top 14 fixtures with Clermont set to entertain Toulouse on Saturday.
Racing-Métro secured a crucial result in the race for the Top 14 play-offs with a bonus-point win over Mont-de-Marsan.
Clermont Auvergne became the first team into the Heineken Cup semi-finals with a 36-14 win over Montpellier.
Clermont are the favourites to book their place in their Heineken Cup semi-finals when they do battle with Montpellier.
The venues for this season's Heineken Cup semi-finals have been confirmed by European Rugby Cup.
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