Retail stocks are only going to get uglier, former department store executive Jan Kniffen said Monday.

"I said last year the fourth quarter is going to be the toughest quarter for retailing," the CEO of consulting firm J. Rogers Kniffen Worldwide Enterprises told CNBC. "It's not better this year."

The S&P consumer discretionary sector has fallen about 2.6 percent from one month ago versus the S&P 500's loss of less than half a percent.

Kniffen said on "Squawk on The Street" that many stores will post bad traffic and same-store sales comparisons this year. Even Black Friday won't be enough to save many struggling companies, he said.

All of this is being driven by "things going online," Kniffen added.

Kniffen said he expects many more bankruptcies, including Sears as early as next month, and said more strategic mergers are likely.

In response, Sears said in a statement: "We remain committed to and have taken steps to reduce costs and continue to execute against our transformation." The statement also said the company is making progress to improve operational performance and to enhance liquidity and financial flexibility.

With the Amazon-Whole Foods deal in the works, retailers are preparing for a "huge battle," Kniffen said. "We're going to see online and brick and mortar merge into one big entity."

"It's not like Whole Foods was a great business, and yet it still got bought by Amazon," he added.

The next big disruption in retail may be pharmaceuticals, he said.

Just last week, Walgreens announced plans to buy more than 2,000 Rite Aid locations. It remains to be seen how Amazon might respond, if at all, he said.

"Wouldn't you go to Amazon to let them full your drugs?" Kniffen asked. "[There's] no reason that can't be done online."

Amazon did not immediately respond to CNBC's requests for comment.

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