It's been a rough month for Chipotle Mexican Grill (NYSE:CMG) investors. The stock has surrendered nearly 7% of its value in March through Monday's close, taking a big bite out of February's rally when the shares rose 12%. That was the biggest monthly gain in Chipotle stock since last July, but that's probably not saying much since the stock has closed lower in six of the eight months following its summertime pop.

March isn't over, and that's more bad news for investors in the struggling burrito roller that until last year was the market darling in the fast casual dining niche. Chipotle stock opened lower this morning after its latest analyst downgrade.

Wedbush Securities is going from ho-hum to hell no as analyst Nick Setyan is slashing his rating on the stock from neutral to underperform. It's at least the third major analyst to talk down Chipotle's near-term prospects. Jefferies and Maxim Group downgraded the stock earlier this month after the quick-service chain put out a gloomy sales update on its traffic trends through mid-March.

Setyan feels that sales are unlikely to recover until 2018, and he feels that Chipotle stock is overvalued in that scenario. To be fair, Setyan had been neutral for more than two years given the stock's lofty valuation until this morning's downgrade. He switched from outperform to neutral on Jan. 24, 2014, meaning he missed out on most of the stock's 28% surge in 2014. He was right not to be bullish during the latter half of last year, of course, when E. coli and norovirus outbreaks weighed on customer zeal, but is now really the time to turn bearish on the stock? 

It's true that Setyan hasn't been a bull on the stock for some time, but he wasn't this downbeat on the shares before. As recently as last month he was telling Investors Business Daily that he was targeting 2017 as the earliest that sales would return to their pre-food crisis level. Now, a few weeks later, 2018 is the new 2017.

The one material incident that has happened since then is that we learned that sales didn't rebound following February's heavy couponing and chainwide closure for a single lunch shift to train its staff on new food safety measures. Even the Centers for Disease Control and Prevention ending its probe early last month didn't get folks to queue up at the burrito assembly line again.

Chipotle warned that year-over-year sales growth declined 28.7% in February if we back out the extra day this time around. The deficit narrowed to 21.5% during the first week of March and 27.3% during the second week, but this still means that we're eyeing Chipotle's fifth consecutive month of double-digit declines in comparable-restaurant sales.

Things should get better from here. Barring any new health scares, Chipotle will be able to discount less aggressively. We're already seeing that as it goes from handing out free bowls and burritos in February to a side of chips with guacamole now. The chain has dug itself into a big hole this quarter, and that's not going to reverse itself entirely during the first quarter of next year. However, with trends likely to improve as 2016 plays out the bar will be that much easier to clear as we dive deeper into 2017. A rough February and disappointing March -- all culminating in what will be Chipotle's first quarterly loss as a public company -- doesn't change that. When Chipotle does recover it will be with a much larger base of restaurants with a greater chance of profitability. Both customers and investors are unlikely to have to wait two years to see that scenario materialize.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.