According to the Washington Post, Gilbert Arenas will miss all of training camp and the first month of the upcoming NBA season. 

Gilbert Arenas confirmed Wednesday that he underwent a surgical procedure this morning that "cleaned out some debris" in his left knee and won't be ready to play for the Wizards until early December. Arenas, who has undergone two surgeries to repair the left knee in the last two seasons, has been limited during the rehab process

What a way to start the NBA free agency period.  Baron Davis unexpectedly opted out of his contract and quickly signed with the Clippers.  Elton Brand also surprised some by opting out, and now is mulling over whether to rejoin the Clips with Davis or travel up north to Golden State.  The offer from the Warriors is actually bigger than the Clippers one for Brand, but his original intention was to give L.A. more flexibility under the cap to go after another star player.  GM Elgin Baylor has done that