He said: "My assessment? Rubbish. Unacceptable for the fans who travelled.
"We talked after Saturday's win over Watford, we talked about needing to keep clean sheets to get results.
"Tonight, every cross that went in we didn't deal with. We looked far too vulnerable.
"I didn't see it coming but it seems to be the story of the season - one step forward and three steps back. It's hurting us.
"It's for other people to decide about my job but it's not about me or my job, it's about the team and as normal after a defeat like that, we ask for a reaction.
"That's unacceptable, it was rubbish but our problems are not just tonight, they're about stopping goals all season.
"At the end of the day, players cross the white line and they have to be responsible for performance, so yeah we sent them out early at half time.
"I felt for the fans tonight, travelling all this way."
Clarets boss Eddie Howe, said: "It was a really good night for everybody and it's given us a lift.
"It was a great start for us and we took the game to Nottingham Forest but I still think we can do certain things better but we're certainly moving in the right direction.
"Our pressing certainly made it hard for Nottingham Forest to play in the first half and the players are beginning to get to know other each other's games.
"There's been such changes at the club that it was always going to take a bit of time.
"Some of the players haven't played a lot of football.
"Jay is a top player and he will only get better. Two goals here and if you add his cup goals to his tally, he's not done too badly with seven goals."
Commenting on his opposite numbers current predicament, Howe added: "Steve (McClaren) has got a fantastic record, he's managed his country. Given time, he'll do a great job at Nottingham Forest."