PINEHURST, N.C. – If a playoff is needed at the U.S. Open, a two-hole aggregate format will determine the winner at Pinehurst No. 2.

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 Pinehurst No. 2, 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 in the same rotation (17, 18, 17, 18 ...)

The 207-yard, par-3 17th has played to a 3.02 average this week, ranking as the seventh most difficult hole. The 448-yard, par-4 18th has played as the week's 14th hardest hole (4.08), considered the most reasonable birdie chance after the two par 5s (Nos. 5 and 10) and two short par 4s (Nos. 3 and 13).