Chances were few and far between for the visitors as the hosts dominated proceedings until Murphy struck to stop his side from dropping into the bottom three.
With just three games to go Richardson believes Stanley's destiny is very much in their own hands.
"The last-minute goal could prove to be so crucial," he said. "It's huge and I think come the end of the season we'll realise how big it is. It wasn't a great spectacle, especially the first half as we didn't come out of the traps at all.
"A few words got said at half-time and we took the ascendancy in the second half and took the game to them. In the end I thought we deserved a point.
"The neutral won't have enjoyed that spectacle, particularly in the first half. They scored and it ignited us, which is disappointing as we shouldn't need anyone to do that. The only good thing to come out of the first half was that it was only 1-0.
"We've got three games to go now and we've got to keep on the crest of the wave. It's still in our own hands. It's important we look after ourselves and get points on the board."