After 62 games, the Sixers have outscored their opponents by 124 points, exactly 2 points-per-game. It's taken some time, but Doug Collins has established an 8-man rotation with a 9th floater at the five. Within that 8 or 9-man rotation, roles have been clearly defined and production has been consistent, for the most part. Of course, in any group, there's a weak link. I think you can probably guess who the Sixers' weak link has been this season.
In a vacuum, I don't put a ton of weight behind plus/minus numbers. Typically, who the player shares the floor with will influence plus/minus to a large degree. When you're talking about on court/off court plus/minus differential, well, then you get into how good a player's backup is as a determining factor.
In Hawes' case, however, the numbers do tell the story. Consider this, with Spencer Hawes on the floor, the Sixers are -54 on the season. With anyone else at the five, they're +178. With Hawes on the floor, the team scores about 4 fewer points per-100-possessions than when he's on the bench. With Hawes on the floor, the team allows about 5 more points to be scored on them per-100-possessions, than when he's on the bench. In just about every way a team can perform, they're worse with Hawes on the floor. Every other player in the Sixers 9-man rotation (with Speights as the 9th) has a positive +/- on the season.
Essentially, Collins makes a gamble every time he trots out the starting lineup. He puts Hawes out on the floor, hopes for the best, then tinkers with the remaining 7 or 8 guys to find a rotation actually capable of competing with an NBA team. The gamble is that the hole won't be too deep for the legit rotations to dig their way out of. Occasionally, the starting five keep their head above water with the Hawes anchor tied around them, from there, it's gravy.
Now this isn't really a dump on Hawes post. If you've paid any attention to the Sixers this season, you realize he's a waste of space. This post is more about recognizing the situation Collins is in for the remainder of this season, the playoffs, and the importance of upgrading the center position this summer.
Against a traditional lineup, with a legit center and PF, the Sixers will always be at a distinct disadvantage on the defensive end, no matter which lineup Collins chooses. With Hawes out there, they're too slow. With Brand at the five, they're too small. Collins has realized that he can make up for these disadvantages, and make other teams adjust to him, by going with the small lineup that sets Thad up to take advantage of huge mismatches on the other end, but when the rubber meets the road, if you stay big against the Sixers, you're probably going to have success.
There is a wild card, here. If Doug Collins can somehow get through to Marreese Speights, and keep him on this track he's been on since the All Star break, he may just have a legitimate "big" lineup he can go to for stretches in the playoffs. Speights gives you so much more on the offensive end than Hawes that if he can just elevate his defensive game to below-average, from dismal, by the time the playoffs come, they just might have a fighter's chance against the Bulls or the Celtics (you don't have to play big to beat the Heat.)
Of course, the remaining 20 games and the playoffs aren't really the big picture. The takeaway from this season, at an organizational level, is Spencer Hawes needs to be given his walking papers. He's not a legitimate NBA center. He's not a legitimate backup NBA center. He's a waste of space.