Harrison Barnes was drafted and immediately crowned as the Warriors' small forward of the future. Starting Harrison hardly puts the team in a precarious position. He, along with Curry and Thompson, complete a trio of fire starters who can smelter any defense in the league. However, with the complexion of the team, and in actuality the league, it may serve the Warriors to bring in Barnes with the 2nd unit as a prime time scorer.
Look at OKC with Harden, or San Antonio with Ginobili. These are successful teams who start players with a penchant for defense, (Sefolosha, Green) while bringing in scorers off the bench to change the complexion of the game. It also provides the 2nd unit with a go-to-guy. Of the players competing for the spot, Brandon Rush has the most talent defensively, (with the exception of KB) and he allows the Warriors to maintain their stratagem of surrounding Bogut and Lee with shooters.
Not only is Rush a good on-ball defender, but he can help David Lee with his weak-side shot blocking. He gained a reputation last season as a guy who can stop people at the rim. He has a talent for erasing shots from behind. If David is being overmatched on the defensive end by the skills of a Aldridge, or the length of a Gasol, it would be nice for Lee to count on Brandon Rush lurking nearby like a tiger, waiting to change the direction of the FGA to the third row. Rush has the attitude to withstand the bruises of the interior when a rebound is in play. He likes contact. This bodes well for the many rebounding battles that will ensue for Bogut and Lee. Rush has a nose for the ball and he doesn't mind getting it dirty when he swoops like Rodan. He'll make for a good clean-up artist.
The Warriors can now proclaim that Curry, Lee, and Thompson are their top 3 scoring options. While the ball is being dominated by the aforementioned players, along with Bogut, Rush's game will not suffer through misuse. He is not tailored for creating for himself so much as accepting the pass and capitalizing. This allows the others to play their game without the retribution of a chemical reaction. The flow of the offense would be seamless.
Harrison Barnes on the other hand, can grow to be a very effective player with the ball in his hands. His scoring instincts will cause much affliction. While Curry, Thompson, and Lee make up the top 3 scoring options of the 1st unit, the bench can field a trio of Jack, Landry, and Barnes. It all starts with Jarret Jack - He has two guys who are perfectly designed for his game. Jack is a wrecking bar on the drive, and no doubt Carl Landry will be the beneficiary of his persistence. Harrison is a kick-out option, and he steps into his shot masterfully from mid-range. Harrison will have more opportunities to create his own shot, and Jack is a veteran point who can set him up. It will be a struggle, but there is a growing confidence that Barnes will be able to create his own shot. These aspirations are not shared by Brandon Rush, which is why he is better suited to glue an offense rather than create it.
Why not Richard Jefferson? Rush is a better defender and a better knock down shooter. Jefferson is also not part of the team's plans moving forward. While he can serve as a solid rotation player, a calm and insightful presence in the locker room, he's not going to be re-signed, and the Warriors have options in Bazemore, Green, Rush, and Barnes, to view and develop. Jefferson is also a player who can shoot you out of the competition if he's having a bad game. His past accolades have given him confidence. This could make him stick out in an unattractive way next to guys like Curry and Thompson - the people you want to be shooting the ball. This is not an assault on Jefferson, but it's hard to envision him fitting in better than Rush or Barnes.
If Barnes is some day to be the starter, it would be best served to give him time to learn and earn. Until then, the strategy of bringing him as a scorer will serve two purposes...