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Shares of the Twitter fell 5.8 percent in Thursday's session after Evercore ISI analysts downgraded the company from "hold" to "sell."
Ken Sena, analyst for Evercore ISI, told CNBC's "Fast Money: Halftime Report" why he believes the risk-reward relative to Twitter's valuation does not make sense.
"I think it's about efficiency for advertisers and I think that the company is acknowledging that advertisers have alternatives now," he said.
Evercore backed its downgrade of the social media company by citing deteriorating user trends and rising competition from Snapchat.
Twitter reported average monthly users of 313 million for the second quarter.
For more details on the Evercore downgrade, check out the CNBC Pro coverage.