First-round draft pick Robert Williams didn't practice with the Boston Celtics Sunday because he missed a scheduled flight, NBC Sports Boston's A. Sherrod Blakely reported.

It's the second mishap Williams has encountered since the Celtics selected him 27th overall in the 2018 NBA draft. He missed his media conference call the morning following the draft after oversleeping.

According to The Athletic's Jay King, Celtics assistant coach Jay Larranaga said the team will deal with Williams' absence internally.

Williams' talent and potential weren't in question heading into the NBA draft. He averaged 11.1 points, 8.7 rebounds and 2.5 blocks in two years with the Texas A&M Aggies.

However, ESPN's Adrian Wojnarowski was among those highlighting the biggest criticism around Williams:

During Williams' introductory press conference with the Celtics, head coach Brad Stevens and general manager Danny Ainge attempted to downplay any early issues with his commitment:

Neither of Williams' infractions is significant on its own, but together they'll likely be a source of frustration for the Celtics. It's the exact opposite kind of impression the rookie will have wanted to make on his new team.

Williams will make his Celtics debut in the NBA Las Vegas Summer League. Boston faces off with the Philadelphia 76ers on Friday.