+/- stats for De Colo are just really bad:
Spurs without De Colo (2266 minutes): +493
Spurs with De Colo (601 minutes): -7
This is the kind of stat that should push Pop to kick De Colo out of the rotation for the rest of the season. De Colo's rookie season hasn't been all bad and he should be better as a sop re but this year might just not be his.
Now, a little stat to help your "Free Mills" campaign:
The best NBA pair this year (minimum 100 minutes played together) is Mills/Ginobili with a +30.5 points scored per 100 possessions:
http://bkref.com/tiny/7ZwxC