With stores from Nordstrom and Apple to Hollister and Coach closed until at least late March, and tens of millions of Americans spending far more time at their computers, it's tempting to think e-commerce can simply pick up the slack for brick-and-mortar chains.

But that would ignore factors like an almost certain sharp economic downturnas nervous consumers digest headlines of layoffs and a swooning stock market; how much traditional retailers have come to rely on their stores to support digital sales; and the wide discrepancy of e-commerce readiness among retailers.

"E-commerce is no savior," warned Neil Saunders, managing director of GlobalData Retail. And brick-and-mortar retailers are likely to face many additional closings, and soon—Mall of America, the biggest in the country, said Tuesday it was closing for two weeks. Bloomberg News on Tuesday reported that foot traffic to U.S. retailers fell 31% in the week ended March 13, before deeper restrictions were imposed. New Jersey on Tuesday ordered all indoor malls closed.

According to the U.S. Department of Commerce, online and catalogue sales represented 17% of total retail spending (excluding restaurant and car expenses) last month. So for all of the hoopla about the growth in e-commerce, the vast majority of retail happens in physical stores. (Still, Amazon said this week it was hiring another 100,000 workers to help it with the surge and on Tuesday said it would halt shipments from marketplace sellers to its warehouses.)

After years of false starts, many retailers finally figured out how to compete with Amazon: use those stores as additional distribution centers, places to return items and fully integrate the digital and the physical in terms of planning and merchandise buying.

Walmart and Target have each spent billions retrofitting stores to enable drive-up online order pick-up and allow them to ship items from their stores that dot the country. Nordstrom, which gets 35% of sales online, uses a growing network of small local stores to make it easier to retrieve an order, or return something without having to go to a big department store.

And it's paying off handsomely for the most tech savvy retailers: Target said that 80% of its online sales growth over the holidays came from same-day services enabled by order pickup in the store or at a drive-up spot right outside one. About half of Kohl's online orders during the holidays are picked up at a store. And Walmart uses its store merchandise to fill most online grocery orders, something that has kept it head of Amazon on that front.

The biggest benefit to these retailers: the heavy use of stores for order pickup and shipping, and product returns cuts down on shipping costs and quickens delivery. Target said recently that the "economics" or the profitability" for online orders was about the same as it is for in-store sales. But for chains that don't use stores as widely or effectively, said Saunders, "online is nowhere near as profitable."

Lucky for Walmart and Target, because they have in-store pharmacies (at Target, they are CVS pharmacy locations) and sell food, they are set to remain open during the crisis.

But Nordstrom, which late Monday said it was closing all its stores for two weeks, and retailers like Gap Inc., which has a $4 billion online business and is also shutting all locations for the time being, will lose key nodes in their e-commerce, hurting their ability to hang on to sales.

Still, companies with a robust e-commerce offerings, which Customer Growth Partners president Craig Johnson defined as having at least 20% of sales come from their online presence, will fare the best in the currently turmoil.

That includes names such as Macy's, Home Depot, Kohl's, Nordstrom, and Williams-Sonoma. But he warned, even the best-in-class chains might be lucky to keep perhaps 40% of store sales lost during a closing.

So the coronavirus crisis is likely to deepen the gap between retail's online winners and its losers. That means those with data-rich loyalty programs that are well connected to apps and the retailer's web site are best equipped to offer shoppers what they really want, or suggest appropriate deals or services. "They know their best customers, they communicate with them," said Johnson.

Put dark stores to work

One way to mitigate the coming pain would be to use stores that are otherwise closed as e-commerce order pick-up spots. That would be akin to what many U.S. restaurants are starting to do: allowing people to pick up to-go orders but not to sit down and dine.

"They could operate the stores but not open them to customers, so have them be dark stores," said Forrester analyst Sucharita Kodali. (Chains including Walmart, Target, Best Buy, and Home Depot have, for the most part, standalone stores, giving them most leeway to use them just for pickup if they do end up closing any stores.)

The analysts agree that retailers still playing catch up on e-commerce will be the biggest losers. J.C. Penney, which is already dealing with an exodus of shoppers and dwindling sales, recently hired a new chief digital officer to finally modernize its site. That leaves the retailer challenged if the company has to operate stores at reduced hours or close them.

CGP's Johnson predict online sales as a percentage of total U.S. retail sales will quickly rise to 20% because of this crisis. But that just means retailers with good sites will lose the least. (Some of that increase will simply be the mathematical result of a lower denominator as retail sales fall, as they likely will at least during the current quarter.) E-commerce laggards will fall further behind.

"If you’re below 10[%] to 20%, you're behind the eight ball" he said.