The Mavs were desperatly in need for a versatile good defender (check), good rebounder (check), able to run the fastbreak with Kidd (check), cut to the basket (check), cleaning up garbage points (check).They didnt want the Suns Marion standing at the perimter jacking up threes or demanding the ball and touches to score 20+. They exactly wanted from Marion the things Marion delivered this season.
But of course if you just see boxscores you probably think that Sefolosha sucks and shouldnt start anywhere in the NBA
RJ on the other hand just sucked most of the time and didnt FIT into the spurs team...