We can talk adjustments all we want, the reality is the Spurs needed to win this game, because of the amount of rest they had going in, the lack of rest they're going to get after it, the fact that Nash was supposedly hurting and the fact that Lopez was out. Plus, psychologically it would have affected the Suns. It's likely that the Spurs just lost not only this game, but this series.
Unfortunately, the Spurs can't guard the Suns like they use to be able to and offensively, they don't have clearly defined lineups to play against them, which they had against the Mavs. Play the three guards and Hill is forced to cover Richardson in the post, which he can't do. Play a guard at the four and Duncan has to guard Stoudemire, which he no longer has the lateral quickness to do.
If you can't slow the Suns, you at least have to dominate them on the boards, which the Spurs can't do if they're closing with Bogans at the four and Mason seeing some time there as well. Between the horrific free throw and three point shooting as well as the fact that they're not a great transition team, the Spurs put a ton of pressure on themselves to score almost exclusively at the rim or from mid range. That's a losing combination. It sounds great to not rely on the three, but when you're this inept at it and you struggle in the other two areas I mentioned offensively, it's going to be tough to beat a team that's as good as the Suns are offensively.