Chipotle is downgraded on fear that its leadership shake-up means earnings may disappoint in the nea

Chipotle Mexican Grill's search for a new chief executive adds uncertainty to the restaurant's earnings trends, according to Blair, which downgraded the shares Thursday.

Even if Chipotle finds a new CEO quickly, the addition of a new leader often results in a costly few transition years, wrote William Blair analyst Sharon Zackfia."While ultimately the move may prove a positive over the long term and accelerate the company's turnaround, it also likely signals that trends remain under pressure and creates more near-term uncertainty until a successor is announced," she wrote Wednesday. "As a result, we are downgrading the stock to Market Perform."

Chipotle announced Wednesday that it has begun to search for a new CEO, with current chief and founder Steve Ells becoming executive chairman. Ells and two others are leading the search, the company said.Chipotle shares rallied on the news of the leadership change and closed more than 5 percent higher Wednesday. Shares closed Thursday down 0.1 percent.