There's value in the bench preserving players in the regular season, but almost any scrub in the NBA could do that. Even if the Spurs lost because of those rest days, Spurs will still make the playoffs.
The only criteria here is determining who will be playing in the playoff rotation.
Last year's bench had 2 players, Belinelli and Baynes. Baynes was there because Splitter was injured, but if he wasn't, then Baynes wouldn't be in rotation. So really only 1 guy in the rotation left the team. ONE PLAYER!
How about this year, the additional player is David West who absolutely will be in the rotation. Come playoff time, will West be more valuable than Belinelli? ABSOLUTELY.