The stock was falling 7.75% to $6328.
Guggenheim analyst Michael Morris downgraded Roku shares to neutral from buy, and lowered his price target to $72 from $77. The new price target reflects more than 9% upside from the stock's current level.
"The Apple video product unveiled on March 25 represents an additional risk to Roku's active user base (even as the platform includes The Roku Channel) while Amazon's (AMZN) - Get Report and Viacom's (VIAB) - Get Report greater pushes into advertising video on demand (AVOD) are increasing competition," Morris wrote in a note.
Apple released in March an entertainment streaming subscription service, Apple TV Plus, which organizes users' choices onto one platform, potentially threatening the value Roku brings to users.
Morris also noted the sale of 100,000 shares from Chief Financial Officer Steve Louden, which "has also shaken our confidence," Morris said.
Roku shares are still up 103% in 2019.
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