So the stage is set for a thrilling finish. Three teams, nine games, two playoff spots.
The Warriors don’t hold any head-to-head tie-breaker. The best they can do is split the season series with Dallas and Denver. Even if they do, they lose out in the second tie-breaker: conference record.
The Warriors’ only chance - other than just finishing with a better record than one of these teams - is a three-way tie. Then the second tie-breaker is record against the other teams that are tied. If the Warriors beat Dallas and Denver, they’d be 4-4 against the two teams combined. Denver would be 4-3 and Dallas would be 3-4. Dallas would be out.
But all that stuff is way too complicated. The best way is just to win more games than one of the other two teams. So let’s breakdown the remaining schedule of each team:

Mavericks Remaining Schedule
at Clippers
vs. Warriors
at Lakers
at Suns
vs. Seattle
vs. Utah
at Portland
at Seattle
vs. New Orleans

Count roadies against Kobe and Nash as losses, especially if Dirk isn’t back yet. Both teams are playing for something. The Lakers aren’t playing that well, but they should get Pau Gasol back any day now.
If you give the Mavericks wins over their scrub opponents, that’s four victories (though at Portland isn’t as easy as it looks, especially with their desperation to finish above .500). Dallas has three other tough home games (Golden State, Utah and New Orleans). Depending on how the Mavericks do in those games will likely determine their playoff fate. Win two, they’re probably in. Lose all three (which is more than possible, especially if Dirk isn’t back or comes back at less than 90 percent), they’re done.

Nuggets Remaining Schedule
at Suns
vs. Suns
vs. Kings
at Sonics
at Clippers
at Warriors
at Jazz
vs. Houston
vs. Memphis

Just giving them wins over their scrub teams, for argument’s sake, they’ll win at least four (Sac, Seattle, LAC and Grizzlies) of their last nine. The remaining five are tough. They’ll probably lose at Phoenix and Utah. But at home to Houston and Phoenix and the road game against the Warriors are winnable. If they pull out two of those three, they’re 6-3 over the last nine and sitting pretty.

Warriors Remaining Schedule
at Spurs
at Mavs
at Grizzlies
at Hornets
vs. Kings
vs. Nuggets
vs. Clippers
at Phoenix
vs. Sonics

They have to beat the Grizzlies, Clippers and Sonics to have any chance. So, again for argument’s sake, put those in the books. Sacramento and Denver at home will be tough games, but they desperately need to win those and should be able to. That would put them at 50-32.
If they can’t beat the three scrubs left on their schedule, and win two home games against quality opponents, they don’t need to get in anyway. That leaves roadies at San Antonio, Dallas, New Orleans and Phoenix. If they can get one of those road games, in addition to the previously mention five games, that’s 6-3 over the last nine and a 51-31 record.