Alberto di Bernardo made all the difference as his kicking condemned Cardiff Blues to a 26-17 defeat at Benetton Treviso.
Di Bernardo kicked four penalties and also converted an early try from Alessandro Zanni.
Cardiff had gone ahead with Ceri Sweeney’s early penalty and retook the lead when he converted Dafydd Hewitt’s try but from then on the home side dominated the first half.
Lou Reed’s try early in the second half was converted by Sweeney but the visitors’ only other score was a penalty by fly half Sweeney.
Paul O’Connell lasted the full 80 minutes as he made a try-scoring return in Munster’s 22-0 derby win over Connacht.
The big lock, who has been out of the game since having surgery to correct a bulging disc in the back, enjoyed an energetic first appearance for Munster since October.
In England’s Aviva Premiership, Christian Day scored a last-gasp try to give Northampton a 26-24 victory over hosts Wasps at Adams Park.
Gloucester’s Freddie Burns broke London Welsh hearts with a penalty five minutes from the end to give the West Country side a 15-14 win over the Premiership strugglers.
London Irish took another step towards Premiership survival with a 26-6 victory over Worcester.