Though Chipotle Mexican Grill, Inc. (NYSE:CMG) shares have risen nearly 6% today, Oppenheimer top analyst Brian Bittner deems Street models to be overreaching and setting the Mexican food chain up for margin shortfalls, “even if the sales recovery proves to be in line with consensus assumptions” of $2.2 million by 2018.

As such, Bittner reiterates a Perform rating on shares of CMG without listing a price target.

“We believe CMG’s poor risk/reward remains problematic for shareholders. Pershing Square revealed a 9.9% ownership, but unlike other activist situations, we don’t see any viable paths to financially engineer shareholder value from the boardroom. CMG remains a hopeful sales/margin rebuilding story, which is at a standstill. Unfortunately, our analysis highlights meaningful risk to Street’s estimates through ’18 and supports our caution,” Bittner concludes.

Bitter ultimately finds himself questioning Pershing’s assessment of CMG shares as “under-valued,” especially “in light of diminishing returns on capital and risks to unit growth.”

The analyst projects EPS for 2017 of $8.78 and $12.01 for 2018, conservatively under consensus of $10.35 and $14.73, respectively.

As usual, we like to include the analyst’s track record when reporting on new analyst notes to give a perspective on the effect it has on stock performance. According to TipRanks, top five-star analyst Brian Bittner has achieved a high ranking of #17 out of 4,147 analysts. Bittner upholds a 71% success rate and realizes 14.1% in his annual returns. However, when recommending CMG, Bittner loses 6.3% in average profits on the stock.

TipRanks analytics demonstrate CMG as a Hold. Based on 27 analysts polled in the last 3 months, 10 rate a Buy on CMG, 11 maintain a Hold, while 6 issue a Sell. The consensus price target stands at $440.35, marking a 1% upside from where the shares last closed.