"The leverage is what's going to kill them," said Bret Wilkerson, chief executive of Property & Portfolio Research.
That means that some malls will be grappling with less income while facing oppressive debt costs.
"You've got pressure from both sides here," Calanog said.
Reis forecasts that the fourth-quarter mall vacancy rate could top 7 percent, the highest since Reis began tracking regional mall performance in the start of 2000.
It sees fourth-quarter mall rents falling by 0.1 to 0.4 percent.
All retail properties, not just large malls, may see their rents fall by an average of 3.5 percent in 2008 and 5.5 percent in 2009, according to Property & Portfolio Research.
The research firm tracks "economic vacancy," or the amount of retail space that surpasses the amount that sales can support.
Economic vacancy now stands at about 13.5 percent and is expected to peak at 17.3 percent in the third quarter of 2009, "implying that one out of every six square feet needs to just go away," Wilkerson said.