McVay has tended to go with the guy who has had the most recent practice in similar situations. Next man up, Evans.
I haven't seen much about his pass pro except comments here, including mine, that add up to "we don't know." If it was weak coming in, I assume he's being coached up. As to how much improvement that has brought, again: we don't know. McVay started Cam and he was close to OK with it.
Royce Freeman can pass protect. And, he can tote the rosk. I'd look for him to get carries if Evans sputters or drops the ball, or if he's needed as the better pass pro guy of the two.
Of the other two guys, of course - Henderson has experience in the system, but when? Could he piull a Baker Mayfield and totally re-up himself with the playbook and new blocking schemes in a couple of days? If so he'd get the calls if used at all. Right now the two newbies are depth and insurance policies until they prove different in practice. They'd have to know the playbook and blow the lid off Evans (who has been on the regular roster all season) to see much action at all before Williams returns. Then, they'll be in competition for the #4 spot or possibly #3. McVay this season has shown a fire for that kind of competition. The team is better because of it.
Meantime, back at the ranch... Evans gets a chance to debut against Arizona, solidify a roster spot behind Williams upon his eventual return, and for the moment move past Rivers on the depth chart. We may see what Freeman brings to this system, and I emphasise this: the coaches already pretty much know. They spotted him behind Evans.
I hope, for the team's sake if nothing else, that Evans brings it on Sunday. Time for the curiosity and speculation to end. I want to see it on the field.