It should have happened a week and a half ago. It could have happened in the summer, if Dirk were the type to play some pickup during the off-hours. Regardless, it didn't, but it's not going to happen in the season either---Dirk Nowitzki had arthroscopic surgery today. Though most reports say six weeks, arthroscopic surgery recovery is typically in the 4-6 week range, so Dirk could be back sooner but obviously they're going to err on the side of caution here.
The question is, if Dirk is out six weeks, what will he miss? Six weeks from today is November 30th, so one of the great pleasures of your Thanksgiving, for our American friends here, should be Dirk carving the turkey (you know, as a prelude. Or whatever). It is exactly 16 games into the season, leaving Dirk to play a healthy 66---which seems pretty good, frankly.
Better news for the Mavericks is who they play in that span. While this includes two games against the Lakers (although don't be surprised that, if all goes well, Dirk suits up for the Nov 24th game), it also includes two games against the Bobcats, one against the decimated Blazers, the Raptors, the Wolves, without Love and also probably without Rubio, the Wizards, the Cavs and the Warriors.
The bad news is, the Mavericks are missing an opportunity to start the season off on a pretty good run---and that Dirk is, again, missing valuable team-building time with a (more or less) entirely new team. It won't be an easy transition for him, for a little while, with no Kidd to take passes from, no Terry to pass to, as he also works himself back into basketball form. Post-return recovery from injury always takes longer than people think. It's also bad news that the schedule will, obviously, correct itself, while Dirk is still trying to get back into form with his new friends.
But the good news, the very good news is, even those Mavs who are still walking (of which Chris Kaman is, again, no longer one), should be able to win about half those games, and it's an opportunity to give the young guys extended burn, and for the new guys to start feeling comfortable as Mavericks.
It's not great. But it could be a Crisatunity. Certainly, it's not time to panic.