The USGA changed the U.S. Open playoff format from 18 holes on Monday to a two-hole aggregate on Sunday, a decision made prior to the 2018 tournament at Shinnecock Hills.
Most of the golf world was introduced to the new format when the U.S. Women's Open needed it earlier this month. It appears Jordan Spieth was a little behind.
Meeting with the media on Tuesday, Spieth was asked what he thought of the new playoff, and he didn't know anything about the change.
"It's the first I've heard of that being an option. It's still 18 holes right?" Spieth said, before being told of the change.
"Oh, it is two. I didn't even know. Either way, I guess strategy changes a little from an entire round. I honestly had no idea that it even changed. I was even looking at a weather forecast for Monday thinking, you know, what's it look like if you happen to work your way into a playoff."
All four major championships feature different playoffs to determine a winner should the need arise.
The Masters has a one-hole sudden-death format, while the PGA Championship and Open Championship can end with three and four-hole setups, respectively.
There hasn't been a playoff at the U.S. Open since Tiger Woods defeated Rocco Mediate in 19 holes on Monday in 2008.