It is interesting that both Smart (-10) and RWill (-13) had "bad" games in terms of +/-.
If you break this down, both were on the court together for 13 min and were -12. For Smart without RWill, 16 min/+2. For RWill without Smart, 9 min/-1. Without either, 10 min/+9. For whatever reason, the team was at its worst when both Smart and RWill were on the court, -11 when one or both were on the court and +9 when neither was on the court. For most of the year, the team would have been at its best when these two were on the court together, certainly at their defensive best.
I hope this is not a trend that continues. History would say it will not continue. I acknowledge that these +/- stats are "noisy". But for this game, this is where the game did turn.