Victory over their fellow strugglers would have taken Posh out of the bottom three, but they trailed 1-0 at the break and in the end it took a late Dwight Gayle goal to rescue a point.
Ferguson said: "We let our standards slip today and the players know what I think.
"We came here to win the game but we played with a lack of intelligence at times and I am disappointed we didn't get the three points."
Peterborough are a point shy of safety, and asked about his side's survival chances Ferguson said: "If we just overtake one or two in the last game to stay up I will be happy.
"Normally if you have 47 points with five games left you would be home and hosed. This season is different. I've no idea how many points we'll need for safety and anyone who tries to predict it is mad.
"This will go all the way to the last game, I'm convinced of that. We have beaten Cardiff twice and taken four points off Hull and we have been very consistent of late. We just have to keep going."