The Clarets were beaten 3-0 at the Stadium of Light, with Parker conceding they never laid a glove on their opponents.
Parker said on Sky Sports: "We were just nowhere near it really. Coming to a difficult place and a difficult stadium against a team who have not lost here. We were never in this game today in any aspect. We've had some good results.
"We looked like a childish team that had no intent about us today. I didn't see a team with purpose or that came to make a mark."
Asked if he felt let down on the night, he said: "Yeah definitely. It's what I stand for. Everything that I stand for in my 20-year career and five years in management.
"I understand that we are in a difficult moment but in this division, more than ever, we need to reboot. We are running out of time. We sit where we sit for a reason. We come back, we try and come back stronger and keep improving."
On only signing one player in the transfer window, Parker added: "Like anything, January comes and there are loads of different variables on whether you can afford players, whether you are able to do that. We go with what we've got. Tonight is about us having a long hard look at ourselves. It's been tough for us."