While the price of West Texas Intermediate has dropped more than 12 percent over the past two months, crude oil could fall even further, commodities expert Dennis Gartman said Monday.

But another downtrodden commodity, , may be poised for a pop, he added.

On CNBC's "Fast Money," Gartman, editor and publisher of the Gartman Letter, said that crude prices will likely be driven lower due to oversupply issues.

"There's an abundance of crude oil," he said. "Prices are probably still heading lower, maybe down to $85 per barrel." That would represent about a 9 percent move lower for crude.

Gartman took the opposite stance on natural gas, which has seen a similar drop in price as oil in the past two months.

According to Gartman, the ability of natural gas to shake off bearish news last week was a bullish signal for the commodity.

"The news last week was a large injection of nat gas into storage," he said.

Gartman said that natural gas initially sold off on the news, but then "turned much higher in a very short period of time."

That reversal, said Gartman, along with a string of warmer weather pushing toward the East Coast, could help natural gas "make its way back to $5, maybe $5.50, over the course of the next several months."

To summarize his point, Gartman reiterated his pair trade in the two commodities. "I think the proper trade is, let's be long nat gas, let's be short of crude oil, one relative to the other."

—By CNBC's Michael Newberg