The 2021 The American Express pro-am format does not consist of two golf tournaments going on at the same time for the 156 professionals in the field, as would typically be the case.
This year, the 156 pros are not each paired with an amateur player, forming 156 two-player pairings. Instead, the field is split into threesomes for each of the first two days. Each golfer will play one round on the host, PGA West's Stadium Course, and the Nicklaus Tournament Course. There will be 78 golfers on each course each day. La Quinta Country Club will not host this year.
The American Express format
For the professionals, the tournament format is simple: the usual 72-hole, stroke-play tournament you see most weeks on the PGA Tour. Lowest score wins.
For the pro-am competition, the individual players are actually on their own. They do not form a team with their professional sherpas over the first three days. There are two competitions happening for the amateurs: a net and a gross competition. On each hole, then, an amateur has two scores: their actual score on the hole (gross) and their score minus their handicap for that hole (net). The total net score for a round is the gross score minus whatever handicap strokes are individually allocated to each player.
The American Express pro and pro-am cut rules
After the first two rounds are completed, the cut rule kicks in, dropping the field to the top 65 pros and ties who advance to the final two rounds at PGA West's Stadium Course.
Prior to 2020, if more than 78 players made the 54-hole cut, then the cut was instead to the number nearest 70 for the final round. It was kind of like getting MDF'd when 78 or more players made the 36-hole cut at other PGA Tour events, except it happened after 54 holes.
Without amateurs in the field, there's no consideration for them in tee times or scheduling on the weekend. Players go out in order of their 36- and 54-hole total scores compared to the field.