The Greens boss, whilst disappointed with the result, was plaesed at the number of goalsscoring opportunities that the side created at Pride Park.
"We gave it our best shot but we just couldn't put the ball in the net and that was the only disappointing thing," Williamson said after the 1-0 defeat.
"We were pleased with our performance but not with the result.
"We got done by a set-piece in the first half and we go away unhappy, but it was a good match, especially in the second half when it was end to end."