Baker, 29, played the full 90 minutes and his deep disappointment at the display was matched by his manager.
"It was an unacceptable performance from the players and none of us are happy with what happened," Baker told the club's official website.
"The manager has made sure we know he's not happy with that. Him, Richard Shaw and Lee Carsley had a right go and it's completely deserved if I'm honest.
"It is not enough from us and we have to improve. I suppose we want it to happen now though in pre-season where we can work on it and get things right.
"The defending wasn't acceptable as we got lads turning their back on the ball which you can't do. You've got to be prepared to take a ball in the face to stop goals."