One Wall Street analyst abruptly changed his view for Facebook shares within hours after seeing a big drop in the internet giant's stock price.
Facebook announced on Thursday major changes to the company's News Feed. CEO Mark Zuckerberg said the internet firm will start prioritizing "meaningful social interactions" versus "relevant content," and that he expects the time people spend on the social network will go down as a result.
That prompted Stifel's Scott Devitt to reiterate his buy rating on the social media firm in a note to clients just after midnight Friday.
"We believe Facebook is doing the right thing for the long-term sustainability of the platform," he wrote. "We believe Facebook shares will struggle until the long-term economic implications of the proposed changes become more clear."
But he said in the note, "We remain buy-rated on FB shares but with less conviction than any previous moment of our coverage."
Then premarket trading began and the shares tumbled more than 5 percent as investors digested the news.
Devitt then sent out a one paragraph note to clients shortly after 9 am ET, downgrading his rating to hold from buy.
"There is too much uncertainty relating to the economic impact of Facebook's pending News Feed changes for us to be comfortable retaining a Buy rating on the stock," Devitt wrote.
Facebook opened lower by 5 percent and was last down 4 percent during Friday trading.
Stifel was the only Wall Street firm to downgrade the stock in the wake of this news. Out of the 45 analysts that cover Facebook, just 5 say it is a hold or a sell. The other 40 say buy, according to FactSet.
— CNBC's Michael Bloom contributed to this story.