If a playoff is needed at the U.S. Open, a two-hole aggregate format will determine the winner at Oakmont Country Club. The USGA announced Sunday afternoon that, due to weather delays during the final round, if needed, the playoff will occur Monday.

The U.S. Open hasn't seen a playoff since 2008, when Tiger Woods defeated Rocco Mediate on a marathon Monday at Torrey Pines, as an 18-hole playoff required a 19th hole. The 18-hole format is no longer, but the U.S. Open has yet to see the new two-hole aggregate model, which was introduced for the 2018 U.S. Open.

In the event of a playoff Sunday at Oakmont, the two-hole aggregate will be played on Nos. 17 and 18. If there's a tie after two holes, the format will move to sudden death, with golfers returning to the 15th hole and playing their way back to the 18th if needed.

The 312-yard, par-4 17th is one of the few scoring holes on the golf course. In 2016, the drivable par 4 played as the easiest hole during the tournament, yielding six eagles and 129 birdies. The par-4 18th will play over 500 yards as it returns to the historic Oakmont clubhouse. During the last U.S. Open at Oakmont, the finishing hole played as the seventh hardest on the course, averaging 0.3 over par.