I have actually played Augusta the day after The Masters, in 1983, in the press day, first off the tee with George Peper. They don't mow the greens the morning after the event, so they aren't tournament-quick. I think I was an 8 handicap then. And of course, I played the course in 1983, when it wasn't 7400 yards and there wasn't any rough.
If I remember correctly, I shot in the mid-90's that day. I didn't play well, but my only real mess was on #15 as Pat Burke suggested ... sitting 100 yards short of the green in two off the downhill lie, and proceeded to make 9 on the hole after two balls in the water. (It still stings.)
Day after The Masters, I think if 100 ten-handicappers started, one of them would break 90, and maybe 20% would break 100 [depends on how freaked out they are by severe greens]. But if you subjected them to the same conditions as on Thursday-Sunday, they are all 5-10 shots worse.
I remember seeing John Harris the day after he competed as an amateur in the early 90's, as Mid-Amateur champion. He said he had played the course a couple of times before, and I said there's a big difference between November and Masters week, isn't there? And he replied that there was a big difference between Wednesday and Thursday.