Amazon (AMZN) is developing its own delivery service, according to reports, prompting concerns about the businesses of shipping-giants UPS (UPS) and Federal Express (FDX). Shares of both companies fell on the news. After all, Amazon is by far the e-commerce leader accounting for an estimated 40% of online sales in 2016.

But it turns out this development may not be as impactful as many of the concerns suggest.

While FedEx and UPS don’t disclose what percentage of revenue comes from Amazon, their exposure is below 10%, according to company representatives and analysts.

In fact, for FedEx and UPS, the “last mile” delivery—which is a big focus for Amazon fulfillment—is actually largely currently carried out by the US Postal Service (USPS).

Bloomberg Intelligence’s Charles Allen added that Amazon has lower “drop density,” or having many delivery points close together, than FedEx and UPS, which could be a disadvantage. As such, most analysts seem to agree that in the more extreme scenarios, Amazon would still be using other carriers to some degree.

“At this time, it would not be cost effective for Amazon to completely replace UPS and FedEx,” according to a recent note Cowen’s John Blackledge.

UPS issued a statement in response to the article, suggesting the news could potentially foster a new opportunity in their relationship with Amazon:

“Amazon is a valued UPS customer. We support all our customers with industry-leading e-commerce solutions and expect to expand these relationships further in the future,” the statement said. “UPS continues to experience topline growth and margin enhancement driven by business-to-consumer volume growth and strong international expansion.”

And while FedEx suggested risks of Amazon’s in-house capabilities in its 2016 10-K, FedEx explained they are well-positioned and said any negative reaction misunderstands the scale and complexity of its business.

“We don’t comment on speculative news stories but there continues to be reporting related to our networks and the transportation industry that demonstrates a clear misunderstanding of the scale, infrastructure and complexity involved in running a global transportation network,” according to FedEx SVP of Integrated Marketing and Communications Patrick Fitzgerald. “FedEx and other transportation providers are innovating as it relates to new services for e-commerce residential deliveries, but that is only one piece of the capabilities that we provide. Demand for our global portfolio continues to grow.”

Online retail is about more than Amazon

Amazon’s $145 billion in US gross merchandise volume, an estimate from Bloomberg Intelligence that includes third-party sales, is still a relatively small share of overall retail volume. Importantly, individual stores and brands like Macy’s (M) and Nike (NKE) are just starting to beef up online efforts to gain share online. A recent Moody’s report, highlighting that online still represents only about 10% of overall US retail sales, suggests there remains much opportunity for online growth at individual brands.

Retailers like Macy’s may not want to cede more share and control to Amazon, which already poses a threat to its business.

While still early, Amazon’s capabilities could be significant. But it may not have all the leverage when it comes to the delivery wars.

Nicole Sinclair is markets correspondent at Yahoo Finance

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