Amazon's offer represents a 27 percent premium to Whole Foods' closing price on Thursday. With Whole Foods shares trading around Amazon's offer price, investors appear to be speculating that another suitor could make a play for the grocery chain.
Among those who could potentially make a bid are Wal-Mart, who has been focusing its dealmaking on bulking up its digital business, and JAB Holdings, a private equity player that has been shifting its focus to restaurants and food and beverage businesses.
Whole Foods has been under pressure from activist investor Jana Partners and money manager Neuberger Berman, which have called on Whole Foods to sell itself. The investors have criticized Whole Foods for its poor performance, and have suggested the chain could be merged with another grocer.