Tesla reported second-quarter results after Wednesday's closing bell, unveiling profits and sales in line with Wall Street expectations. Losses mounted for the stock, however, as the company's call with analysts sowed more doubts than offered answers about Tesla's prospects and Chief Executive Elon Musk said he could see potential for "a few rough quarters" ahead.

Nelson downgraded the company’s stock to a neutral rating in April. But even some of the Tesla bulls on Wall Street are saying that the time for Musk to take action is running out.