Thank you. My guys are grinders, they are always playing, except for the big tourneys. Then they are OUT.It's a big field (156) but there aren't a lot of exemptions. It's basically the top 60 players in the OWGR as of two or three weeks before the tournament. Varner's highest ranking this year was 73. There's a few other exemptions (major winners the last 5 years, past US Open champs within the last 10 years, multiple tour wins between Open's, players who made the Tour Championship the previous season), but the only other way in is through qualifying. The qualifying is tough. 36 holes in one day, usually 70-80 players per site for 3-5.
Mickelson wasn't qualified until he won the PGA (but the USGA offered him a special invite).