Alex Waller apologised to the Saints supporters after Sunday's 'dreadful' defeat at Kingston Park.
Jim Mallinder's men surrendered a 24-10 lead to lose 46-31, conceding five tries in the second half and seven in total.
It was a shocking result for Saints, who slid down to eighth in the Aviva Premiership standings.
And Waller said: "It was dreadful.
"It wasn't the performance we were after in the second half.
"There is lots to look at and we need to look at ourselves in the mirror really.
"We played into their hands a bit. We didn't need to play a loose, expansive game - we just needed to play in the right areas of the pitch.
"We got dragged into playing that loose game and they're very good at it.
"Full credit to them - they've got some very dangerous backs and they exploited our mistakes."
And Waller has assured the Saints fans that he and his team-mates felt their pain when it came to the second-half performance.
"It has hit us hard," he said.
"We started very well and to put in a performance like that second half isn't good enough.
"I can only apologise to the fans because that's not what we expect of ourselves and I'm sure they expect more of us as well.
"Rest assured we're all hurting a lot more than anyone would think.
"We've got plenty to work on on Tuesday morning."