I'm a very average golfer. Im content with a round in the 80s and that's on pretty simple courses. And that's never playing the ball "down."
If given two mulligans per shot, I think Spieth would easily beat me by double digits. Especially if we are playing a PGA Tour quality couse under PGA Tour conditions (fast greens, tall rough, playing ball as it lies, etc.).
These guys are just too good.