Chipotle Mexican Grill Inc. is parting ways with Chief Marketing Officer Mark Crumpacker, who struggled for years to restore the burrito chain’s image after an E. coli outbreak.

Crumpacker, who has worked for Chipotle since 2009, is stepping down on Thursday, the company said. His exit follows the arrival earlier this month of Chief Executive Officer Brian Niccol, a Taco Bell veteran who is expected to overhaul the business.

“We have a very talented marketing team in place and we’ll continue our existing programs while we finalize the plans for a new CMO,” Chris Arnold, a spokesman for Chipotle, said in an email.

Crumpacker had the difficult task of piloting Chipotle’s marketing efforts after a wide-ranging food-safety crisis in 2015. Multiple foodborne-illness outbreaks sent sales — and Chipotle’s stock price — into a tailspin. Though the management team made progress on turning around the company, the comeback has been slow going.

The executive also faced personal problems. In 2016, he was put on leave after being arrested on cocaine charges. Crumpacker returned to work later that year after completing a rehab program.

Niccol replaced Chipotle founder Steve Ells as CEO, a dramatic changing of the guard for a company that was long criticized for its clubby and insular leadership team. Crumpacker, one of the top five executives at the restaurant chain, was a high school friend of Ells and credited with designing Chipotle’s logo. Ells remains chairman of the Denver-based company.

Crumpacker also helped land a job at the company for his partner, Tim Wildin, according to a New York Times interview in 2011. Wildin worked as the brand director for Chipotle’s Asian-food offshoot, ShopHouse, which was closed last year.

Last July, Crumpacker attempted to generate marketing buzz by enlisting the Wu-Tang Clan’s RZA to tout Chipotle’s so-called clean menu. But the effort was overshadowed by an outbreak at a restaurant in Virginia.

In another wrinkle, Crumpacker has taken jabs at his new boss’s former employer: Taco Bell.

In 2015, as Chipotle was touting its simple ingredients and the removal of GMOs from its menu, Crumpacker made a thinly veiled reference to all the additives in the food of its taco rival. He told analysts that there were 85 ingredients in a “single fast-food burrito served by one our competitors.”