Boston Celtics center Tacko Fall was limited in practice and out for the team's season opener against the Philadelphia 76ers at the Wells Fargo Center on Wednesday with a concussion. Ahead of the game, the Celtics rookie explained to what caused this concussion. 

The 7-foot-5 center said he was going to wash his hands after a workout at the team's practice facility, the Auerbach Center, and hit his head on what he called a "low ceiling" that he had not noticed. 

While he noted that the ceiling was low, anyone who is not well over seven feet tall probably would have cleared it no problem. No doubt Fall has spent most of his life ducking under doorways and into cars, but this time the ceiling won. 

Fall said he hit his head but at first did not notice anything was off. He went on with his day with no concussion side effects, going to his swim lessons event at the Charlestown Boys and Girls Club and practicing at the Auerbach Center.

When he woke up though, he felt off and, according to head coach Brad Stevens, he was, "A little under the weather." 

Stevens added that he was being careful.

"Tacko got hit in the head yesterday after individual work," he said. "It sounds like he's being very cautious about that."

He entered the NBA concussion protocol, but was able to be around the team during practice, travel with them for their first game and is "very close" to returning, according to Stevens. 

From now on, Fall will be extra careful around "low" ceilings.