Darren Ferguson's side made a slow start to life back in the Championship despite playing some good football but after beating Reading and then Newcastle in the space of four days they are now on a high.
Williams said: "You just can't put a limit on our potential. It's quite frightening really because we are improving all the time so who knows how far we can go?
"We have certainly hit some form lately. No-one in the team was surprised because we felt we had been playing well and not getting the results our performances deserved.
"But we have kept faith with the way we play and now we are getting our rewards. We are playing some great, fluent attacking football and we are so fit and fast we are starting to run over teams.
"We had a lot of confidence before we won these last two games, but there is also no danger of us getting over-confident. The manager keeps our feet on the ground."