Simon Grayson says Sunderland's defeat to Barnsley was 'unacceptable' and claimed too many of his players did not play for the team.
The Black Cats began the game well but never responded to Ike Ugbo's opener.
Sunderland failed to test Barnsley in a woeful second half showing, with goalkeeper Adam Davies only required to make one save.
Grayson said: "It is unacceptable to lose in the manner that we did. Too many players wanted to do their own individual stuff rather than working for the shape of the team and working hard for each other. Barnsley found it quite easy from the first goal. One or two need to take responsibility and work harder for the team.
"For 25/30 minutes we were the dominant team, played really well, had some good opportunities. Against the run of play we concede and from there on Barnsley deserved to win, because they did the basics better, they ran further, harder, put their bodies on the line. That’s what it is about, too many of ours didn’t do that after the opening third."
The Sunderland players were given an angry reception as they left the field at the end of the game, something Grayson saying he had no problems with.
"Rightly so. I’ve no problems with that. We could have been in front but Barnsley hung in there, did what is required to win games. They won the second balls, scrapped and knew somewhere along the line they’d get the chances to score.
"It ruins my plans for the next two weeks, I hate seeing a team cave in as such. We have to make sure we put things right, I'm passionate about what we do and what the club means to the travelling supporters, we want to give them something to cheer about. It's alright ]he players] enjoying the trips to Norwich when it goes well but when you're under pressure, as we told them we would be because of how hard Barnsley, you've got to dig deep and do what's required to win, we didn't today."