Investors are putting too much attention on Square's bitcoin ambitions, Citron Research's Andrew Left told CNBC's "Fast Money" on Wednesday.
The well-known short-seller was on to talk about Square, cryptocurrencies and Alibaba, the Chinese e-commerce giant.
Earlier this week, Left tweeted that "WallSt. drunk on Bitcoin nonsense." He put a short-term $30 price target on shares of Square, the card payments processor co-founded by Jack Dorsey. The stock was down 6 percent in aftermarket trading on Wednesday, after the company said second quarter earnings per share could be lower than what analysts are expecting.
Square began offering bitcoin trading in the first quarter but said it only netted revenue of $200,000 from the activity. Bitcoin, Left said on Wednesday, "keeps the focus away" from Square's core business. Payments processing "has a long-term trajectory of contracting" margins and faces stiff competition.
He has been more positive about Alibaba, which he calls a compelling growth story. "It's the anti-Square," he told Fast Money. "It's the tollbooth to the Chinese middle class." Shares of Alibaba were up 0.6 percent in afterhours trading.