IMHO:
The time for a fixed starting line-up is gone. Depending on the opposite team, Spurs will start two bigs or just one (Aldridge will rest at some point). It makes sense to insert Cunningham as starter vs Lebron, Durant, George and other teams with an All-Star SF and only 1 big in their lineup.
It looks like Gay is working well offensively as SF and he did a good job against James in the last minutes yesterday. Rudy looked healthy again but he didn’t in Portland. He will struggle against SGs playing at the 3 position, running through screens side to side and guarding them in off the dribble pick&roll shooting situations.
Guards rotation is a question mark as well. What’s going to happen when White returns? Is Forbes earning legit playing time? What about Walker?
Popovich has innovated many times already, sometimes just transferring coaching strategies from College Basketball or European Basketball. In Europe, starting lineups are totally flexible, with players coming in and out depending on coaching adjustments for every specific game. The Spurs installed the habit of resting stars and Popovich often inserted third string players as starters. Veteran players and injuries made Spurs use multiple starting lineups in the past two seasons. This variable starting line-up is simply the next natural step.
Maybe I’m wrong. What do you think?