McCann told BBC Radio Cambridgeshire: "We had a couple of hours chat with the gaffer and everyone put forward ideas as to what we need to do better.
"A lot of things came out in the open and there were some home truths, which is what is needed sometimes."
Despite beating Stockport 4-1 in their FA Cup first round replay on Tuesday, Posh have lost four of their last six league matches, including the 5-1 defeat to Charlton at London Road on Saturday.
McCann, who made the move from Scunthorpe over the summer, believes they have allowed poor training sessions ahead of the weekend to impact on their performances.
I started off quite well, but more recently I've been disappointing and I'll hold my hands up to that
Grant McCann
"The last couple of times we've been beaten, we've been poor in training on the Friday and that's overlapped into the Saturday," he said.
The 30-year-old has been an automatic pick for Johnson so far this season, but admits he is one of a number of players whose recent form has not been up to standard.
"I started off quite well, but more recently I've been disappointing and I'll hold my hands up to that," he said.
"Everyone will go off form from time to time and after Stockport I think I'm on the way back."
Source: BBC Sport
Source: BBC Sport