I guess what was confusing me was that in the previous game, the 2 reserves didn't play very much.
So in this game, it was also the fact that the starting PF got into foul trouble, and then the game was a blow out in the 4Q.
When the starting PF, Winters, was in foul trouble early, the coach looked for his backup, Olaya, but he was already in at SF. So he then just look over all the other players and picked Castillo - not because he was the backup at SF, but because he was the best available PF. And then when he was thinking about giving Olaya a rest at SF, he saw that his backup, Castillo was in at PF, and the reserve Bustos wasn't in good enough form or skills enough to come in, so Olaya stayed in at SF.
Then in the mop up time in the 4Q both starters at PF and SF were benched. At that time Castillo came in as the backup at SF, and Bustos came in as the only remaining forward at PF.
If Sardo were still on the team, he would have seen more action at PF, because of the foul trouble, and Castillo would then have been available to spell Olaya at SF?