But substitute Joe Anyinsah's 66th-minute tap-in condemned Paul Ince's men to their third straight defeat, even though Carlisle's Tom Taiwo was shown a second yellow card in stoppage time for kicking the ball away.
"It was not good enough - I can't defend people," Robinson said. "In the first two minutes, we could have been 2-0 up but then we were 3-0 down through our own faults.
"We've had an inquest and that will stay among us. Luke Chadwick showed what a good player he is, as two or three did, but we need at least eight players performing well.
"We had no desire to win the ball in the air - defending is all about a willingness to get hurt. I will watch the match again, as will the manager, and we will try to rectify it."