It might have something to do with TIE, but perhaps not stamina. You were leading by 20 going into the 4th, and that's about the point where the Match Engine will pull your starters and let your bench play the entire 4th.
I just checked the final quarter. In the first few minutes, my team was down 9-0. Most starters were actually playing.
I still wonder how strong the stamina effect is.