Chairmen from the 11 remaining top-flight teams will meet at Hampden tomorrow to vote on whether to allow newco Gers back into the top division next season.
The Ibrox side's bid to transfer their league share from the old Rangers company is likely to be rejected, with a number of clubs already indicating they will vote against the plan.
But former Ibrox captain Ferguson insists the financial implications could soon hit home hard.
"If Rangers go out of the Premier League it will have a massive effect," he said. "Fans might not realise how big Rangers are and how important they are to the league.
"When Rangers travel to the likes of Fir Park and Rugby Park, we used to sell out most of their stadiums. Some clubs might only sell one stand and the rest of the crowd is Rangers fans.