Snap stock has all but given up the ghost.

The social network was worth $31 billion after its public debut in March 2017. Now it's less than $8 billion.

The stock took another tumble Wednesday, dropping 13 percent in its worst performance since May, after the hasty exit of Chief Financial Officer Tim Stone just eight months into his role.

Erin Gibbs, portfolio manager at S&P Global, says watch out below, the worst is yet to come.

"We do not see this as necessarily the bottom," Gibbs said on CNBC's "Trading Nation" on Wednesday. "The fact that your CFO is walking away from 80 percent of the stock that he got as a signing bonus is a clear indication of how he thinks the company is going to go."

That's not all that has Gibbs worried about Snapchat's parent company.

"The earnings estimates are actually going even lower in the past month and they weren't that stellar to begin with," she said.

Snap is expected to post a net loss of 19 cents a share when it reports earnings on Feb. 5, according to analysts surveyed by FactSet. In the same quarter a year earlier, it had reported a net loss of 28 cents a share.

"Certainly the stock could go farther down, and I wouldn't say that this is the point to get in," added Gibbs.

Stacey Gilbert, market strategist at Susquehanna, says her firm also has a negative view on the social network.

"Our internet analyst Shyam Patel had a great call on this," Gilbert said on "Trading Nation" on Wednesday. "His concerns … continue to be that ad buyers are not seeing the return on investments that other platforms like Facebook and Instagram are doing and users are fleeing."

Options activity suggest Gibbs and Gilbert are not alone in their doubts over Snap's future performance.

"The flow we're seeing is really more consistent with those that are protecting short positions, not any one positioning for longer-term growth here," said Gilbert. "This is a negative. We're avoiding it."

Snap is one of the most heavily shorted stocks on Wall Street with short interest at 23.7 percent of its float.