(REUTERS) - The tallest players in the National Basketball Association (NBA) may be able to reach for the sky, but Boston Celtics rookie Tacko Fall found out the painful way that even without a ball in his hands he cannot beat a low ceiling.

The 2.26m centre was placed in concussion protocol after banging his head while washing his hands after a workout at the Celtics practice facility last Friday (Oct 18), Massachusetts-based website MassLive.com reported.

The 23-year-old from Senegal missed Boston's season-opening 107-93 defeat by the Philadelphia 76ers on Wednesday (Oct 23) as he had entered the league's concussion protocol two days earlier after experiencing delayed symptoms.

"Tacko got hit in the head after individual work. He was a little under the weather. It sounds like being very cautious about that," Celtics coach Brad Stevens said on the eve of the match.

He added on Wednesday that Fall, who had signed with the team as an undrafted free agent in July, was expected to make a recovery "real soon".

NBA protocol requires a player to be without any concussion symptoms at rest. A doctor will then evaluate the player and put him through a "return-to-participation" exertion protocol before a team doctor and NBA's concussion programme director clear him.

Fall was the headliner at the draft combine this year with the longest reach (2.496m), standing reach (3.105m) and height with shoes (2.31m) since the NBA began recording statistics in the 2000-01 season.

He is joint fifth in the list of tallest NBA players ever, behind only Gheorghe Muresan and Manute Bol (both 2.31m) and Shawn Bradley and Yao Ming (both 2.29m).