The visitors found themselves two goals down after just eight minutes and it could have been worse if the hosts had taken their chances.
“We did not start bright, we let two silly goals in, one from a set-piece and another penalty,” Kewell said.
"But we showed great character to come back into the game and I felt from that moment on we kind of dominated the first-half.
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"We were looking exciting, we were passing, moving, creating spaces and opportunities and I think we got a fair enough opportunity to get back in at 2-2 so I was pleased at half-time.
"For ten minutes Chesterfielf had the two goals and they had another clear chance and then we settled into the game. We had to change a few things around but when we worked certain areas we looked great.”
The defeat leaves the Bees second bottom of the National League table with no wins from their first six matches.
But Kewell, who was appointed during the summer, believes there are positives they can take from their performance at the Technique.
"I can’t complain about my players, they worked hard tonight,” he added.
"We are getting there, we are finding our feet, but again we have got to stop some little individual errors.”