Gregory told dcfc.co.uk: "Sometimes I think its best not to play a promoted side because they play on a wave of enthusiasm, they can have a winning mentality.
"Everything at Reading has been geared towards winning for the past twelve months. We saw what happened when Bolton first went into the Premiership last season, it was good to miss them early on as they were beating everyone and they went top of the league.
"We don't want to play a promoted side early on but we've got Reading first game. But we must show we're worthy favourites to get back into the Premiership, it's a tough game but we're ready for it."
John Gregory joined Derby in February after resigning as manager of Aston Villa. The Englishman battled to save the Rams from relegation but despite some encouraging results there was too much ground to be made up and Derby were relegated to the Nationwide League.