"But it's no excuse for us.
"It's been a really busy spell for them, but the importance of an Old Firm game, I'm sure, will cover any tiredness or fatigue that they feel."
Rangers have already lost to Edinburgh outfits Hearts and Hibernian and another defeat would leave Smith's side with much to do even this early in the campaign.
"After losing two games in the league, it doesn't matter to us whether it's an Old Firm game or otherwise, we can't afford to lose many more," he admitted.
"We have put ourselves under a bit of pressure in that respect.
"Whether it's Celtic or any club, we've got to go out and start to show a consistency in the league that will enable us to make a better challenge."
