In short, the race for Captain's Picks is pretty wide open with Mickelson a pretty good favorite to get 1 if he doesn't crack the top 9.
The current top 9 seem like they would be locks even if 1 or 2 slip outside the 9 guaranteed spots. Assuming the top 9 stay the same, that leaves 3 Captains picks up for debate. Leading candidates based on OWGR would seem to be:
#29 Webb Simpson
#30 Patrick Reed
Todd and Kirk, at #12 & 13 on the RC point list currently, also deserve consideration as they have seen their OWGR improve from 186 & 60 to 41 & 43.
Given that everyone on the above lists rank has dropped this year except Reed and Na, I think Phil will get a captains pick unless he looks completely out of sorts between now and the end of the PGA. Moore, Kirk and Bradley were the only Americans outside the top 9 that finished ahead of Mickelson at the Open.
I think Woods gets a Captain's Pick if he has a Top 10 by the end of the PGA or gets 2 Top 25s.
I think Stricker gets strong consideration for a Captains Pick as he hasn't missed a cut this season and hasn't finished worse than t35. Of course, skipping the Open with the RC in Scotland doesn't show that he is fully committed.
With his last 3 finishes all in the top 12, Ryan Moore seems to be finding his game at the right time to get some strong consideration if he keeps up his good play.