The investment firm also lowered its price target to $90 from $151.
At last check Twilio shares fell 2.3% to $94.73.
Piper Sandler is still bullish on Twilio's long-term prospects, estimating that its direct-to-consumer product could more than double revenue to $2 billion over the next five years,
But Piper Sandler lowered its 2020 growth estimates to 10% year over year from its previous view of 31% growth.
"Unlike a traditional seat-based software-as-a-service model, TWLO has a unique revenue recognition model tied directly to traffic volumes (messaging, voice, e-mail, authentication, etc.)," the firm's analysts wrote.
"The combination of a usage-based model coupled with exposure to some of the largest digital natives (Uber, Lyft, Lime, eBay, Shopify, etc.) that have been directly impacted by Covid-19 elevates near-term disruption risk to the growth trajectory."
Last year, the company's top-10 customers, which include companies in the list above, accounted for $153 million in revenue, a 28% year-over-year increase.
Those companies are especially susceptible to the coronavirus, and that makes visibility on Twilio difficult, according to Piper Sandler.
"The global scope of the virus disruption, which has been particularly severe for some of Twilio's largest digital native customers within the transportation and travel sectors, outweighs the direct-to-consumer secular tailwinds longer-term, in our view," the firm said.