The inauspicious NBA debut of Celtics rookie Robert Williams continued Sunday as he missed a flight and subsequent practice in advance of the start of Summer League.

The unexcused absence came several weeks after Williams overslept and missed a news conference a day after the draft, in which the Celtics chose the 6-foot-9 center 27th out of Texas A&M.

Williams was considered one of the best athletes in the draft, but questions about his maturity and commitment led him to slip.

Celtics assistant/Summer League coach Jay Larranaga downplayed the incident, but didn’t exactly let Williams off the hook either. As reported by MassLive.com:

“I think everyone’s disappointed,” Larranaga said. “You want to get everything off to a good start in the first day, but we’ll handle that internally and move forward. We’re excited for him to get here (Tuesday) and get started.