Now that Deron Williams and Mark Cuban have exchanged cross-Atlantic jabs, can we get back to the real reason the All-Star point guard didn’t go to Dallas?

As Williams said after he re-upped with the Nets, he feared what would happen if he had signed with the Mavericks and Dirk Nowitzki went down or declined.

It’s pretty hard to debate that case at this point in the aftermath of the Dirk-less Mavs being beaten convincingly by FC Barcelona Regal.

Oh, it’s not the end of the world to lose an exhibition game to a European team. The Boston Celtics aren’t canceling their season because they lost to a Turkish team.

One loss for the Mavs, even to a team without a ton of NBA talent, after a little more than a week of work together isn’t worth worrying about too much. As much as Cuban liked the moves made to build a short-term supporting cast this summer, it’s not like anybody believes the Mavs could be a playoff team without Nowitzki performing at an All-Star level.

So save your concern for Nowitzki’s sore, swollen right knee that prompted him to watch this game from the bench.

The Mavs are surely being cautious this early in camp, but we saw early last season how bad Nowitzki could look when his knees bothered him. He altered his offseason conditioning routine to address the problem, but Nowitzki is also a year older with another season’s worth of mileage on his 34-year-old legs.

You can no longer expect Nowitzki to stay strong all season if he has to play heavy minutes and carry the Mavs’ offense on his back.

That’s why GM Donnie Nelson and coach Rick Carlisle wanted to sign a superstar in the first place. They hoped Nowitzki could slide into a less taxing co-star role for the twilight of his prime.

After the Mavs missed on Williams, they managed to add a couple of post-up threats in Chris Kaman and Elton Brand and a pair of penetrators in O.J. Mayo and Darren Collison. Cuban keeps trying to convince people -- himself? -- that the sum of those parts is greater than one All-Star point guard.

With or without Williams, one thing is painfully obvious: The Mavs aren’t nearly good enough without a healthy Nowitzki.