City were put to the sword by a dominant Notts outfit, who led early on through David McGoldrick’s opener.
The hosts cut through the visitors at will at times and a three-goal blast in the final ten minutes of the half saw City trail 4-0 at the interval – with Macauley Langstaff (2) and Dan Crowley finding the net with City jeered off at the break by their understandably irate 2,300 visiting contingent.
Alexander changed shape at the interval and his side at least showed character and renewed fight in the second period and pulled two goals back.
But the damage was done as City succumbed to a third successive league loss for the first time since last Christmas.
Alexander acknowledged: “We were nowhere near in the first half. The scoreline shows that. We were way too passive and I’ll take my fair share of the blame for that.
"I did not hammer them (players) at half-time. I hold my hands up and the first half completely went wrong. Not from every stat, but from a scoreline perspective. We had to start again.
"I set us up to be compact and it wasn’t the case. Notts County cut us open several times, but we still had opportunities to score. We did not take those opportunities and they scored a couple of goals in quick succession.
"We had to make sure we won the second half and we played in a different fashion and were much more front foot.
"There was massive pressure on us coming out with a massive backing, despite the game being on Sky and they would have been asking a lot of questions about the players – and myself – about the mentality. The second half has to be a benchmark going forward.”
Having no truck with criticism from fans, who also vented their spleen in the direction of owner Stefan Rupp and called on him to leave the club, Alexander added: "Rightly so. They weren’t happy, understandably so and we weren’t happy, make no mistake.
"It wasn’t a positive experience at all, but the supporters showed that if we give them something and we show fight, endeavour and a different attitude, then they will get behind us.”
For a fourth successive league game, City conceded an early goal in the first few minutes, with a concession of six goals in the opening 15 minutes of league matches representing the second-worst record in League Two.
Alexander said: "We have to look at the first ten minutes as a different game.
"We just have to make sure we don’t concede and put the opponent on the back foot until the game calms down. But wehn the game foes calm down, we are one-nil down. And there’s happened in the last four games.
"If it’s one or two, it can be unlucky, but four on the bounce is a little habit. The first goal is so crucial and the statistics in English football show you that."