So, let's see if I can follow your logic.
We made 35 shots out of 90 attempts. If we take Brandon's and Blake's attempts and makes - this leaves us with 17 out of 51. Since Blake and Roy do have some assists recorded - let's take this from the total - this leaves us with 8 out 42 made.
Now, you have just told us that Roy and Blake monopolized the shots - it is clear that this was an amazing offense there in the 7 minutes Sergio was in - what with shooting 42 times in 7 minutes. Since there were supposedly also 8 shots going in during that time - and Sergio had only 2 assists - it is clear that someone else has done a magnificent job of creating these shots during these magical 7 minutes (which surprisingly, did not see a + in the +/- stats since we know it was -4 during these magical 7 minutes - meaning that the Suns have made at least 2 more shots during these 7 minutes.
This analysis, based on your assumptions leads me to believe that the best PG we have on the team is not Sergio who got only 2 of the 8 made shots in the 7 minutes - maybe it was Greg...
Unfortunately, we also know that the Suns made at least 10 shots during these 7 minutes - leading me to think that your assertion that Sergio is a good defender is absurd.
See - even if I try to play by your funny hallucinogenic analysis - Sergio comes out looking pretty bad.
The fact of the matter is that Sergio did not have an awful game - it's just that we had 2 players with a good game - and they were Roy and Blake - so they had to stay in the game.