Tries from Bruce Reihana and Ben Foden, added to five points from Shane Geraghty and a penalty from Stephen Myler proved enough to win the first game in Pool 1, Edinburgh's group, but there were far too many errors for Mallinder's liking. "It was a tough game, Castres played very well and were very physical and we didn't play well," the Saints boss said. Asked about the reasons for the poor performance, Mallinder said: "You want to get on the front foot but our lineout didn't function tonight. "We were unfortunate to lose lock Christian Day very late in the day through food poisoning and this affected our lineout calls." Northampton's goal-kicking in the first half was abysmal with four misses from Reihana and one attempt from Geraghty which barely got off the ground and which may have proved crucial on another day. Mallinder said: "The goal-kicking was frustrating, both had off-days but last week Bruce kicked four from five and the week before that Shane kicked four from five." "Allowing Castres a bonus point was not ideal but I'm confident we are still a good side and can go to Edinburgh next week and get a result. "We won ugly tonight but I'm confident we will do well in this competition and qualify for the next round." In Pool 6 Glasgow beat the Dragons 21-13 at Firhill.