Andrew Left is bearish on shares of Roku, the maker of TV streaming devices, at their current price level.
The noted short-seller debated with Needham's Laura Martin about the hot stock on CNBC's "Halftime Report" Wednesday.
Martin raised her price target to $50 from $28 for Roku shares on Monday, sparking a rally for the shares this week.
"You're talking about an extremely hot market. A highly shorted stock and a note that puts a big target on it. We've seen this so many times," Left said. "I'm sure we'll see the stock trade right back to … $28."
In response, Martin said Roku could be "Netflix all over again" in terms of potential upside for investors.
Shares of Roku traded up 0.4 percent Wednesday $46.63. A drop to $28 represents a potential decline of 40 percent for the stock.
Left called Roku a "total joke" on social media Tuesday and Needham's bullish Roku research report "irresponsible." The investor confirmed he has a short position in Roku shares Wednesday.
Roku declined to comment on Left's negative thesis.
The streaming-media-player maker's stock jumped 68 percent on its first day of trading as a public company in late September.
Left gained notoriety for successful bets against stocks such as Valeant Pharmaceuticals. He is known for his bearish company-specific reports published his website Citron Research.