Wall, a 22-year-old point guard that led Washington in scoring last season, was diagnosed with the early stages of a stress injury to his left patella but will not require surgery, the Wizards said in a statement.
"We feel fortunate that we caught the injury early and that he will be able to return with the vast majority of the season still in front of us," Wizards president Ernie Grunfeld said.
Wall, taken first overall by Washington in the 2010 NBA Draft, had been experiencing discomfort in his left knee and the injury was discovered during an examination on Thursday.
He led Washington in scoring (16.3 points per game) and assists (8 per game) last season while starting all 66 games during the lockout-shortened campaign.
The Wizards begin training camp on October 2 and open the 2012-13 NBA season on October 30 at Cleveland.