Forwards coach Phil Dowson has warned Saints they still have a lot of work to do after they eased past Harlequins on Friday night.
Taqele Naiyaravoro and Teimana Harrison both scored twice, with Mike Haywood also dotting down as the black, green and gold bagged a bonus-point 40-22 win at Franklin's Gardens.
It means they stay top of the Gallagher Premiership, having won all three league games so far this season.
But Dowson was in no mood to rejoice, insisting Saints' second half showing was 'disappointing'.
"The first 38 minutes were excellent but we conceded just before half-time and for the rest of the game we were battling," Dowson said.
"We were under a huge amount of pressure for most of the second half, which was disappointing because we were so good in the first half.
"To put an 80-minute performance together is the goal and the dream, but we have to keep battling away to eradicate some of those mistakes we made in the second half because further down the line and in different competitions and against different opposition, we'll get punished.
"We were way off in the second half in terms of what we were trying to do.
"It was almost the reverse of last week, when we were sluggish at the start and we really found our feet in the second half. We started really well but didn't manage to get into our stride after that.
"We've been really pushing hard and with the World Cup coming to an end tomorrow, players are playing for places and we've been talking about that consistency, which is maybe what we lacked in the second half.
"We've talked about having high standards and there are a lot of games left this season.
"When things do start to go against us, we're going to need to make sure we've banked some points before.
"I'm obviously being hypercritical but I'm also delighted for a lot of those players on the pitch tonight."