Shares of Office Depot and Staples plummeted Wednesday, as analysts called into question the office supply chains' ability to effectively compete in the market as stand-alone companies.

Following a judge's decision that the two companies may not merge, Office Depot — which was downgraded by Jefferies from "buy" to "hold," and from "neutral" to "sell" at UBS early Wednesday — fell about 40 percent to below $4 a share. Staples stock, which was downgraded by both Jefferies and UBS from "buy" to "hold" status, tumbled more than 18 percent to below $9 a share.