On Friday, shortly after Jeff Bezos and his team announced Amazon's big vision to shake up the grocery industry and acquire grocer Whole Foods, these big-box retailers' stocks tumbled , with shares of Target falling more than 10 percent at one point.

Deutsche Bank on Monday lowered its rating for Costco specifically to hold from buy, saying the competitive advantage from its Food Business is at risk due to Amazon.

"The WFM acquisition represents a game changer with COST's competitive moat in grocery under greater threat while its digital platform lags peers, putting membership renewal at risk for decline," Deutsche Bank analyst Paul Trussell wrote in a note to clients.

"I think this [deal] is certainly a game changer," David Lebovitz, a global market strategist for JPMorgan, said during an interview on CNBC Monday morning.

"If I was a shareholder of Target I would be terrified," Tom Forte, managing director of Maxim Group, told CNBC in an interview on Friday.