The Mavericks have been the source of many jokes about failures in free agency, whether as a result of the DeAndre Jordan fiasco or with multiple players using them as leverage to get big deals elsewhere, the Mavericks have just not been able to land the big fish of the world. This past offseason they did finally land one of their targets with Harrison Barnes, which has resulted in more jokes due to the size of his contract, but there is no way around it, the Mavericks were the 2nd big winners behind the Warriors which is, of course, ironic due to their winning being a result of the Warriors.
Dallas was the perfect landing spot for Barnes
Simply put, other than staying in Golden State, there was nowhere that Barnes would (in theory) be better off. In all likelihood, he was aware of this when he signed his offer sheet with Dallas, but he will have a great mixture of finding a new home where he can expand his game, without having all the hopes and dreams of a franchise hoisted upon him immediately.
The big thing that makes Dallas such a great place for Barnes is Dirk. Dirk will (hopefully) still be very prominently featured in the offense, and likely will still be the man taking most of the crunch time shots, this means that Barnes will not be forced into being the focal point of the offense from day one. He has spent the early years of his career playing a very small role on a stupidly talented team, and even if he does have the ability to be the featured guy in a good offense, it would be very difficult to just flip a switch from one role to the other so quickly.
On top of the basic fact that Dirk will still be taking plenty of shots to keep the pressure off of Barnes, is the shots that Dirk doesn't take. One of the secrets to Dirk's greatness is (and always has been) the incredible spacing he provides. The friendly spaces that come about due to Dirk's incredible shooting have been a career-reviver for several different players over the years, and when you throw in Wes Matthews as the starting SG, Barnes should have plenty of space to operate when creating looks for himself and others.
Lastly is that, even though Deron Williams is not awesome, he is a perfectly serviceable starting point guard, and JJ Barea is another decent option off the bench, as is Devin Harris. Similarly to how Dirk will be able to keep too much shot making duties from falling onto Barnes right away, having a few capable (if not great) ball handlers on the team will also help keep Barnes from getting too much put onto his plate too soon.
All of these things combine to mean that Barnes is able to play to his strengths that he showed with Golden State, where he can be a very good shooter and off-ball player, and pick his spots to create for himself and others. It could end up being damn near a perfect balance of him being able to take on a larger role, without being forced to take on more than he is ready for.
The Mavericks could be awesome on defense
This is a point that I have not seen brought up nearly enough, the Mavericks will be starting Wes Matthews and Harrison Barnes on the wing and Andrew Bogut will be the starting center. Matthews and Barnes should pair up for one of the better defensive wing pairings outside of San Antonio, and Andrew Bogut is still one of the best defensive players in basketball. The other two starters, Dirk and Williams, are not that good defensively (especially Dirk) but they are both veterans who can at least keep from dragging down their teammates.
There are a couple of question marks here of course, first off the Mavs need to manage to get similar production out of Bogut as Golden State did, while only playing him low 20s minutes per game, but keeping him mostly healthy all season. The other question is Wes Matthews, who did not look 100% all of the last year, which is understandable given that he tore his Achilles, but at this point, he should be back to 100%, the question is where 100% is for him now.
Assuming it is back up to where he was before the injury the Mavs are in business. If there is a noticeable dropoff, though, there could potentially be some issues.
The last question is who else will play center behind Bogut? Since Bogut is not going to play 30 minutes per game all season, the backup center minutes are more important for Dallas than most teams. Sala Mejri will be an interesting guy to watch in this role, he blocked tons of shots and is a decent rebounder but did not play enough to really know if he is much good. Dwight Powell did not play a lot either, but he showed some real promise and is a super athlete if a bit undersized as a center.
Whoever ends up taking the bulk of the minutes, the Mavericks will need to find a reliable 2nd string behind Bogut, because whether by choice or not, he will likely spend more time on the bench than most starting centers.
Dynamic wing combo
The last thing that should give Dallas lots of hope for the future is their pair of wings in Barnes and Matthews. Assuming Matthews is pretty much back to the player he was before the injury, the Mavericks legitimately can boast having (probably) the 3rd best pair of 2-way wings in basketball, trailing only the Spurs and Warriors.
Both Barnes and Matthews are hugely flexible and well-rounded players who can guard multiple positions on defense, shoot the ball, and create for themselves.
It is not known for sure how much longer Dirk will play if he wants to he will have a chance to be the greatest old guy player in NBA history. But whether he goes with the Brady plan of “Play until you suck” (which I am hoping for) or just gives it another year or two and hangs them up with some still in the tank, the Mavericks can feel comfortable that in the future they can build their team around 2 players that are easy to build around because of their flexibility.