Akwasi Asante’s ninth goal in a Blues shirt won the game for the Spireites five minutes from the end in a match they controlled for large parts.
The victory leaves Town five points behind Eastleigh who occupy the last play-off spot, but Strevens’ side have played two more games.
“Chesterfield have been on a really good run and they deserved their victory tonight and they are getting themselves into a position where they are going to be starting to think about hitting the play-offs now,” Strevens said.
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“I did not think we were good tonight, I did not think we were anywhere near the standards that I expect from them.
“We got to the point where we were nowhere near at it but we should come away and get a nil-nil draw whether we would have deserved it or not.
“Joe (McDonnell) did not have lots of saves to make but they were better on the ball than us, we were poor with the football tonight.”
The visitors were caught out by Chesterfield’s slight tweak in formation which created a ‘box’ in midfield of Curtis Weston, Martin Smith, Jack Clarke and Tom Whelan with Asante leading the line on his own.
“We started the game brightly and the plan was to get the ball down the sides of their three centre-halves because they play a system we have played so we know the areas to exploit,” Strevens added.
“But they changed their formation and changed personnel, they freshened it up from the game they had on Saturday, and they have got the squad size to chop and it worked for them. They have been playing a 3-5-2 and they changed it to a three with a box in midfield and one up top and it caused us problems. That is why we had to change it at half-time to try and nullify that and we did for the most part without being good.
“When you get to the 86th minute and concede in the manner we did, it is a terrible goal and I am going to make sure I show the boys it so they can analyse it because that is not a goal we should be conceding.”