Dallas Mavericks
1 Biggest problem: The offense is still a work in progress
Roughly through the first 10 games of the season, the Dallas Mavericks are likely where most expected them to be at this point. Signing Klay Thompson was always going to bring about some growing pains and that's very much what we're seeing from this team. Even though the Mavs, individually, have one of the most prolific offensive starting 5s in the NBA, I'd argue that the team's biggest problem at this point in the season is that they still don't have a clear identity on that end of the floor.
Even with the addition of Klay during the offseason, the Mavs are still ironing out their offensive flow. They have great individual talents but are still learning how to play as a team on that end of the floor. Right now, the Mavs are an average offensive unit. And if they want to emerge as an NBA Finals contender, they'll need to begin to click on that end of the floor before the stretch run toward the postseason.
Denver Nuggets
1 Biggest problem: The lack of a reliable bench unit
I'll be the first to admit that after a shaky start to the season, the Denver Nuggets have been much better of late. But even though the Nuggets have begun to play better of late, this is still a team that ranks toward the bottom of the league in bench scoring. At this point, their lack of a reliable bench unit has to be considered the team's biggest problem. If the Nuggets are going to reemerge this season as a legit championship contender, they certainly have some things to figure out off their bench.
The issue is, I'm not sure how the Nuggets are supposed to solve this problem. The hope was that Russell Westbrook could emerge as their secret weapon off the bench but he's been too inconsistent so far this season. A trade can't be completely considered off the table but they'd likely have to trade one of their core contributors to get something done. To be quite honest, I'm not sure the Nuggets are ready to pull off such a move.