Asked whether he believes Musk, who has failed many times to deliver on Tesla forecasts, analyst Colin Rusch said "no."
"We discount what he says pretty substantially," he added.
But Rusch said he's still a believer in the overall Tesla story because it's innovating at a faster rate than traditional automakers. "It's about the cool-car thesis," he said.
The electric car maker was not immediately available to respond to CNBC's request for comment on Rusch's criticism of Musk.
Electric vehicles are the future and they're fun to drive due to great handling and acceleration, Rusch said. And with traditional automakers slow to cannibalize their combustion engine vehicles, he thinks it's going to be hard for them catch up to on electric, despite the production problems plaguing Tesla's new Model 3 sedan, its first vehicle aimed at the mass car-buying market.
"If they solve the problem of getting a Roadster to … [space], they can probably do the same with providing guidance to us on timing. But they're not," Rusch said, referring to Musk's other company SpaceX, which earlier this week launched a rocket carrying a Tesla Roadster sports car to demonstrate payload capacity.
Rusch appeared on "Squawk Box" the morning after Tesla posted its biggest quarterly loss ever but promised to meet short-term and long-term goals for the Model 3, which starts at $35,000. (Tesla's loss excluding one-time items was smaller than expected and revenue was slightly better than estimates.)
"What I heard last night is they're hedging their production times. We're not totally buying that," Rusch said. Tesla doesn't really know how to solve the issues and "we expect them to have ongoing problems."
Tesla said Wednesday evening it's on track to produce 5,000 Model 3s per week by the end of its second quarter, a twice-delayed goal that the electric car company had originally projected for the end of 2017. The Model 3, with a starting price at $35,000, is Tesla's first vehicle aimed at the mass market.
Musk continues to expect to make 1 million vehicles annually by 2020.
Rusch said Tesla needs to own up "to the fact that they're facing very serious problems." But he added Tesla remains well ahead on electric vehicle innovation, which makes the stock interesting.
Rusch has a perform rating on the stock but doesn't have a price target. The highest price target among the Wall Street analysts who cover Tesla is $500 per share.
Tesla closed 3.3 percent higher at $345 per share Wednesday. It was down nearly 2 percent in early trading Thursday.
On Wednesday morning, a big believer in Tesla told CNBC she believes the stock will one day trade at $4,000 per share. Ark Investment Management CEO Catherine Wood, a money manager known for making bold calls, added, "Our bear case is $600."