It’s a crowded leaderboard at Torrey Pines for the final round of the 121st U.S. Open.

As everyone starts to ponder potential outcomes, the word “playoff” comes to mind.

There have been 33 playoffs in U.S. Open history, with the most recent coming at Torrey Pines in 2008. You may have heard of this one. It involved Tiger Woods on a broken leg defeating Rocco Mediate in extra holes after the two had already played an extra 18 holes on Monday.

U.S. Open playoffs had always involved an extra day for extra holes. There was once a time they played 36 holes, and one even went 72 holes.

But that all changed in 2018, when the U.S. Golf Association adjusted playoff formats for the U.S. Open, U.S. Women’s Open, U.S. Senior Open and U.S. Senior Women’s Open.

At the time of the announcement, USGA CEO Mike Davis said: “There is no right or wrong way to determine a winner in stroke play. … Two holes will allow a player to recover from any single mistake, and at the same time, provide a memorable, and perhaps dramatic, experience for all involved.”

According to the USGA, here’s how a playoff would work:

In the event of a tie after 72 holes, a two-hole aggregate playoff will take place following the completion of Sunday’s final round. If the playoff results in a tie after two holes, the tied players would immediately continue to play off hole-by-hole (sudden-death format) until the champion is determined.

The two-hole aggregate playoff would start on No. 7 then go to No. 18. If there’s still a tie, sudden-death golf would be on Nos. 7, 8, and 18 until someone wins.