You just can't ask more from Murray at this point. Everything was working for him. It's not reasonable to expect him to do that against teams without terrible D, but he could go down a few pegs and still be an impact offensive player. The biggest change this year to me has been his added bulk.
Not sure why we can't expect more from him and I don't see the Rockets defense as the only reason for Murray's good offensive game. First, his confidence in that jump shot has made an extraordinary leap from where he was in his first year and the mechanics and footwork look solid. In addition, the kid is tough as nails going right at Harden and Westbrook and I would expect the same kind of performance when he faces the elite teams. Another improvement is finishing better at the rim, which is probably directly related to increasing his strength and effectively using that lightening quick speed and length. We've only seen the tip of the iceberg when it comes to his offensive game and he will only get better as the year goes.

I hope Pop realizes Walker has to be in the rotation. Beli certainly has his benefits, but Walker's upside is amazing. Forbes is playing entirely too well to unseat at the moment, but the starting two-guard spot is Lonnie's eventual home. Harden isn't nearly the challenge to defend as people might think (you just have to be okay with him making some really inefficent shots and focus on not fouling and not giving up great threes by overhelping), but he's already at least as good as Simmons ever was on that end for the Spurs. He also played a pretty solid offensive floor game. He didn't shoot well, but it's clear he can get to so many shots most players just can't find an angle for. You add in solid D and good passing? I don't see how you can overlook him. He's not going to be perfect, but he seems like the guy you want running with Mills, White, Carroll/Gay and Poeltl. At least let him play himself out of the role. You can even disguise it as "saving Beli for the home stretch".
Totally agree that Walker needs to play. His defense really shined in this game and is light years better than Marco and his offensive game will only get better. You could make an argument that he has the best all around offensive game on the team.