One of Tesla Motors' most bullish supporters in the financial community said Tuesday he expects the automaker to fall short of its goal of 55,000 vehicle deliveries for 2015. Morgan Stanley automotive analyst Adam Jonas cited concerns about the timing of the Tesla Model X SUV launch and Tesla’s ability to rapidly build up the car’s inventory and fill back orders before Dec. 31. Tesla watchers will look to CEO Elon Musk to address these and other questions following the company’s first-quarter earnings results due in early May.

"Heading into the earnings call, we continue to look for more details surrounding Model X execution -- in particular, launch timing, speed of ramp [up] and order backlog," Jonas said in a research note Tuesday. "Given the significance of this launch, we don't expect Tesla to cut any corners and believe Elon Musk and management are fully willing to sacrifice short-term profitability [via higher-than-expected up-front costs] to ensure a successful debut."

Morgan Stanley maintains an overweight rating for Tesla, which means it expects the stock to outperform the industry, with a 2015 target price of $280. Tesla's shares (NASDAQ:TSLA) dropped 1.11 percent to $207.44 in Tuesday's afternoon trading.

As a growth stock company investing heavily in expanding global production, sales and support, Tesla Motors doesn’t need to show a profit anytime soon. But one of the most important measurements of the company’s ability to reach its target of 500,000 vehicle sales by 2020 is the growth in deliveries over time. If Tesla misses a target, investors start to worry.

The Palo Alto, California, maker of the Model S luxury electric car said in a regulatory filing April 3 that it delivered 10,030 Model S sedans to customers in the first three months of the year. But that number included 1,400 vehicles that were supposed to be delivered in December but were delayed by “customers being on vacation, severe winter weather and shipping problems [with actual ships],” the company said in a February letter to shareholders.

The unforeseen delay means Tesla was able to count those cars in the first quarter, and analysts cheered that the company had exceeded prior forecasts for first quarter deliveries, pushing Tesla’s stock price higher. The company’s share price is up nearly 8 percent since the delivery number was released earlier this month.

For Tesla to meet its 2015 guidance of 55,000 cars, it will need to deliver an average of nearly 15,000 cars per quarter through Dec. 31, not a little over 10,000 including some layovers from last year. During a company conference call in February, Musk said he was “pretty comfortable with achieving on deliveries.”

But Jonas said he expects Tesla to come in this year at 51,000 vehicle deliveries, including 3,100 Model X SUVs, most of them in the last three months of the year. Last year Tesla downgraded its annual deliveries from 35,000 units to 33,000, citing a temporary halt in production to add capacity to its sole Fremont, California, factory. It could announce a similar adjustment later this year, especially if the Model X release is delayed for a third time.

Tesla wound up delivering 31,655 units last year, up from 6,892 cars in 2013, news that knocked more than 6 percent off the company’s share price on the day the number was announced.

Tesla will report financial results of its first quarter ended March 31 after markets close on or near May 7. Tesla will likely announce the definitive date by early next week. Analysts polled by Thomson Reuters expect Tesla’s losses to grow to $113.4 million, from a loss of $49.8 million in the same quarter last year. Revenue is expected to ring in at $1.03 billion, up from $713.1 million. Tesla could report its first billion-dollar quarter in revenue terms if it meets this forecast.