The Argentine star missed a chance to kick Leinster further ahead but the home team got another boost in the 25th minute when Toulouse forward Gregory Lamboley was sin-binned as the visitors defended desperately in their own 22.
If thuggery and violence continues to follow the English team around France their next game is in Toulouse on June 22nd the English Football Association should pull the side out of the tournament.
Cardiff were beaten by Toulouse in the inaugural Heineken Cup final in 1996, the only time a Welsh team has qualified for European rugby's showpiece club occasion.