4 key holes that will decide the U.S. Open at Erin Hills

The 117th United States Open is being contested at Erin Hills Golf Club this year - the first time the facility has hosted a professional major championship.

Here are four key holes that players will have to navigate this week at the Open.

No. 4 - Par 4, 439 yards

Bob Lang, the course's former owner, relocated the No. 4 green prior to the 2011 U.S. Amateur, moving it back on top of a dune. Lang's reasoning was that the previous putting surface rewarded poor approach shots - which isn't the case now. Any approach that's struck too firm will end up in the hazard behind the green.

No. 9 - Par 3, 135-150 yards

The shortest hole on the course requires just a straightforward wedge or 9-iron, but the difficulty begins if a player misses the green. The putting surface is surrounded by seven steep bunkers and thick fescue, while the hole is usually played into a left-to-right crosswind from an elevated tee. Any shot blown away from the green will likely result in a bogey or worse.

No. 15 - Par 4, 252-370 yards

No. 15 is a driveable par 4 for most of the competitors, especially if the USGA decides to move the tees up for one of the rounds. Long fescue lines the left side of the fairway, while deep bunkers can be found in the fairway and around the putting surface. During the 2011 U.S. Amateur, Patrick Cantlay decided to lay up, but found the fairway bunker off the tee, leading to a bogey. Cantlay would lose his lead, and ultimately the match to Kelly Kraft.

No. 18 - Par 5, 622-675 yards

The elevated tee shot generally plays with the wind to the players' backs, meaning they'll gain extra roll on the firm fairway. The long hitters will likely try to go for the green in two shots, but any attempt that comes up short and left will end up in fescue or in one of the hole's 20 bunkers.