Investors delivered a stern message of disappointment to Facebook and Twitter (TWTR) when they posted debut quarterly scorecards following their IPOs. Twitter shares cratered 24% the following day, while Facebook’s tumbled 11%, drops that stand to this day as the biggest one-day losses for both.

The options market is already positioned for a double-digit swing in Snap shares by the end of this week.

One key to Snap, the owner of the wildly popular Snapchat messaging app, dodging a similar reception from the market rests on whether its user growth and engagement measures meet investors’ expectations as Facebook aggressively copies its most successful features.

The earnings report and subsequent conference call after the bell “will be make it or break it” for Snap, said Eric Kim, co-founder and managing partner at Goodwater Capital.

The stock, which started trading in March in the largest tech IPO since Facebook’s in 2012, jumped 44% on its debut, but has since fallen 5.5% from that day’s closing price.

FOCUS ON USER GROWTH

Wall Street expects Snap to post a quarterly loss of 19 cents per share, according to Thomson Reuters (TRI). Analysts expect revenue of close to $158 million, roughly four times the $38.8 million figure from a year earlier, but down about 5% from $165.7 million for the fourth quarter of last year.

But investors will focus on Snapchat’s user numbers and how the service is holding up against encroachments by rivals.

In recent months, Facebook has launched Facebook Stories, a near-identical clone of Snapchat’s most popular feature, also called Stories. The feature lets users post a string of videos and photos that disappear after 24 hours and is also available on other Facebook services, including Instagram and WhatsApp.

“Much of the call should be around Stories as it represents the bulk of Snap’s future value given the importance of video advertising to the company’s relatively nascent business model,” Goodwater’s Kim said.

Facebook (FB) recently announced that Instagram Stories alone had reached 200 million daily active users (DAU), eclipsing Snapchat’s year-end overall DAU count of around 161 million.

J.P. Morgan (JPM) expects Snap’s first-quarter DAU to grow to 169 million, while Monness, Crespi, Hardt & Co is targeting 173 million.

Snap (SNAP) still may have an edge over Facebook with its active user base aged between 18 and 34, many of whom visit more than 18 times a day and are a highly coveted group for advertisers.

“Our favorable outlook on Snap stems not only from the company’s ability to innovate and cater to millennials in high value markets, but also capture publisher content and consumer mindshare as video consumption grows on digital,” said James Cakmak, an analyst at Monness, Crespi.

A POPULAR SHORT

Despite a modest rally in Snap shares in recent weeks, short sellers—who aim to make a profit by selling borrowed shares and buying them back at a lower price later—have not let up in placing bearish bets, according to Ihor Dusaniwsky, head of research at financial analytics firm S3 Partners.

“We saw $100 million worth of short selling in this past week, ahead of the earnings and Snap short interest stands at $946 million, which is the highest level since the IPO,” he said.

Meanwhile, options market activity suggests a swing of about 13.5% in either direction by Friday, based on the price of certain options expiring this week.

“Snap’s option activity was bullish last week, but the bears came out in greater force just two days before earnings,” said David Russell, senior manager at online broker E*Trade in Chicago.