Two goals in the first-half and a missed penalty resulted in the Lions dropping to 23rd in the National League table, writes Tom Feaheny.
"I had no complaints, we know that the culture, the mindset that we want to change, we have put a lot of work into it, but we didn't do the basics right I'm afraid," Cox said.
"I feel like I need to make some big decisions, my expectation levels are high, I'm okay with a loss if the performance and effort is there, that wasn't the case during this loss, it wasn't good enough
"Everything we wanted to improve upon just wasn't there, in recent games it has been, we just need to make sure this was a one off."
They aim to make history on Sunday and reach the third round of the FA Cup for the first time as they travel to Mansfield Town.
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