Michael Nolan is out as Smashburger CEO less than a year after taking over the reins of the fast-casual burger chain. Nolan, a former Panera Bread Co. and Corner Bakery executive, left the Denver-based company last week, a Smashburger spokeswoman confirmed Wednesday. The company offered no explanation for Nolan’s departure. Tom Ryan, who co-founded Smashburger in 2007 with Rick Schaden, will move into the CEO role, the fourth person to hold that title since 2013. “Tom is re-engaging with the company to ensure its continued passion for great food and great guest experience,” Smashburger said in a statement. A food industry veteran, Ryan had begun to take a more active, day-to-day role at Smashburger.