Unless Green is having a very off-night, he should play more minutes than Manu at this stage. A less Manu is a better Manu for Spurs. The missing free-throw notwithstanding, Manu becomes less efficient when he plays too many minutes and is asked to initiate the offense too much.
Also, Pop has to settle down on one backup PG, at least for each game. I feel that Mills played relatively well, but he got no playing time in the second half.
Last one is the most critical one to Spurs' playoff hope. That's when/if Tony cannot penetrate like he wants, what's plan B?