I have 828 play-by-plays from last season where the final margin was single-digits and for which the play-by-play has clean substitution data. “Clean” meaning that according to the play-by-play there were five players on the floor at all times. (This does not necessarily mean it’s accurate. There are probably some glitches as the curiously low figures immediately after halftime indicate.) Below is a graph of the average starters per team that were on the floor in those games, and the percentage of time that the entire starting five was on the floor.
There’s been a lot of research on lineup construction in baseball, but to my knowledge there isn’t much going on in terms of how to best deploy one’s players in basketball. It’s a given that your best players will start the game, and it makes sense to distribute a player’s time on the floor across the entire 40 minutes of the game. However, it seems like the enterprising underdog could use a predictable substitution pattern to its advantage. (I’m just saying it seems like it. I’m not exactly sure how.)
Almost every coach is giving their starters a rest sometime between the 8 and 13 minute mark of the first half, especially if that starter is a big man. And the starting lineup really doesn’t play much together. At any given time after the second media timeout of the first half, the starting lineup was on the floor in less than 10% of the cases examined, bottoming out at 4% at the 11 minute mark of the first half. You have Thad Matta to thank for those cases. (I kid.) Other than the first 5 minutes of the first half and the first four minute of the second half, the average team’s starting five is usually not on the floor.