Spurs need another "scorer", which by definition does not rely on one facet of his game (i.e. 3pt shot) to put the ball in the hole. Maggette was heavily coveted because he can score in multiple ways and that's something the Spurs were missing when Manu lost some of his speed because of the injury.
Phil Jackson made it a point to close out on the three point shooters and gave the Spurs no space to operate on the perimeter. If the Spurs had one or two guys that were adept at putting the ball on the floor and pulling up inside the arc, they'd have faired much better.
Hopefully Hill and Hairston (if he makes the team) will be able to bring a "scorer" mentality and look to penetrate if given the opportunity.
I'm not sure Mason brings that "scorer" aspect, but then again I don't know enough about him to say he can't be that "scorer". Guess we'll find out...