TROON, Scotland _ The British Open is only played at Royal Troon an average of once every 10.33 years, so a primer about the course might be helpful to fans following the tournament.
First, when you wake up Thursday, don't be surprised to see a slew of players at 3 to 5 under par.
Next, check how many of those early leaders have actually finished their first round, and for those who haven't, see how much of the back nine they have played.
To say Royal Troon's back nine is more difficult than its front is a major understatement, like saying last season's Cavs were better than the Sixers.
Troon's nine outbound holes are along the shores of the Firth of Clyde, most are pointed in a southeasterly direction and Troon's usual wind direction is generally at the players' back.
Troon's inbound nine holes usually play into the wind. The 3,745-yard back nine is 300 yards longer than the front nine, but the back nine is an aggregate par 35 while the front is par 36.
In past British Opens at Troon, the average front-nine scores have been three to four strokes lower than the back nine scores.
"As you flip through the middle of the golf course, it's very difficult just to hit greens in regulation," Jordan Spieth said after one of his practice rounds. "I had to put two really good strikes on it to get it on the green."
As of Wednesday, the forecast called for a mostly dry Thursday with mild (for Scotland) 10-15 mph wind, a much more wet and windy Friday and a relatively dry, but gusty Saturday.
During practice rounds this week, players experienced Troon's usual northwesterly wind, but also a couple of days when the wind switched directions.
But if the wind blows its usual direction, long hitters like Dustin Johnson, Jason Day and Rory McIlroy will have a huge advantage on the first few holes, which include a couple of shortish par 4s, No. 1 at 370 yards and No. 3 at 379 yards.
"I can drive up next to the green (on No. 1) and same on 3; I can get it there if it's downwind," Johnson said Wednesday.
If the wind is blowing the usual direction, Johnson said the par-5, 560-yard fifth hole will be, for him, driver and 5-iron to the green.
It's a course of split personalities. Every player in the field will feel pressure to play the opening nine in several under par because of the wickedness of what awaits on the back nine.
The first reality check actually arrives one hole before the turn, on the par-3, 123-yard No. 8, the "Postage Stamp" hole _ so named because of the diminutive green, set in the side of a sand hill, surrounded by five bunkers.
It's the hole that 71-year-old Gene Sarazen aced during the 1973 British Open, but also the hole on which German amateur Herman Tissies made a 15 during the 1950 Open.
During a practice round this week, McIlroy made an 8 or 9. He lost count after it took several attempts to escape one of the back bunkers.
"If you make four 3s there this week, you're probably going to gain a bit of ground on the field," McIlroy said.
Colin Montgomerie, 53, is in this week's field and, in fact, was scheduled to go off in Thursday morning's first group and hit the tournament's opening tee shot.
Montgomerie's father, James, was Troon's longtime secretary. The house Montgomerie grew up in was a short walk from Royal Troon.
"You play the first seven holes relatively downwind," he said. "And the (No. 8 tee shot) is the first shot you've got into a wind. It doesn't matter what standard of golf you are. It's different. It's a change. You haven't done this for two hours.
"Self-doubt comes in. And hesitation. It's a great hole."
It's a warmup for what awaits on the back nine. In 2004, the last time the Open was played at Troon, seven holes on the back nine ranked among the nine most difficult of the tournament.
The par-4, 451-yard No. 10 ranked as the third-hardest. The 482-yard 11th, which for the pros was changed from a par 5 to a par 4 starting with the 1997 British Open, ranked first with a 4.41 scoring average. The 430-yard, par-4 No. 12 ranked as the third-most difficult.
The diabolical No. 11 is named "The Railway" because train tracks run right of the fairway, separated by a 4-foot stone wall. Shots that bounce off the wall are permitted, but any ball that goes over the wall is out of bounds.
Both sides of the fairway are framed by thick gorse, leaving little margin for error. During the 1962 British Open, won by Arnold Palmer, Jack Nicklaus made a quintuple-bogey 10 there.
When Justin Leonard rallied to win the '97 British Open with a 6-under 65 in the final round, he started his charge with a six-birdie, one bogey front nine.
But it was Leonard somehow shooting 1-under on the back nine that Sunday while other contenders faltered that ultimately won Leonard the tournament. He made par-saving putts of 10 feet on No. 11 and 15 feet on No. 15.
That is the roadmap that this year's Champion Golf of the Year must follow, just like Troon's eight Open winners to date.
Make a lot of birdies on the front nine.
And survive the back nine.
