William Blair analyst Sharon Zackfia downgraded Chipotle Mexican Grill to Market Perform from Outperform after the company announced that its founder and CEO Steve Ells will step down following the completion of a search to identify a new CEO. While a new leader may accelerate the company’s turnaround longer term, today’s move likely signals that Chipotle’s trends remain under pressure and creates more near-term uncertainty, Zackfia tells investors in a research note. The analyst adds that transition years, in which costs accelerate before sales trends rebound, often follow new CEOs. As such, she’s more cautious on Chipotle’s earnings recovery trajectory following today’s announcement. The market, on the other hand, is applauding the company’s decision. Chipotle shares in premarket trading are up 5%, or $15.12, to $300.98.