Rory McIlroy signs autographs during a practice round for the U.S. Open golf tournament Wednesday. McIlroy and the other golfers in the field will have to navigate a beast of a course at the Congressional this weekend in what could turn out to be one of the wildest U.S. Open events in years.

BETHESDA, Md. — When Rory McIlroy and his practice buddies got to the bottom of the hill on the 18th hole at Congressional, they didn’t all rush for the green or the bunkers that surround it.

Instead, they stopped and played pitch shots from 50 yards and in. The safe play. A good idea for a U.S. Open setup that figures to give very little and take away a lot.

That’s pretty much par for the course for the tournament the USGA so fondly describes as the toughest test in golf. This year’s Open begins Thursday without the sport’s biggest star, Tiger Woods, and with no fewer than 25 or 30 legitimate candidates to become champion of a tournament that only occasionally plays to the favorites.

At 12-1, Phil Mickelson and the world’s top two players, Luke Donald and Lee Westwood, were the front-runners in Las Vegas. McIlroy, who collapsed at the Masters after holding a four-shot lead heading into Sunday, was next at 16-1. Charl Schwartzel, who ended up winning the green jacket, was 50-1.

Most times, the only surprise at the U.S. Open is if there isn’t a surprise.

“When I won in ‘94, I think you guys must have thought I was the biggest surprise in the history of the game,” said Ernie Els, who had never won in America before he captured his first major at Oakmont.

More on topic this week, though, was Els’ second U.S. Open win, which came in 1997 at Congressional Country Club — a beast of a course that normally hosts congressmen and Washington’s power set, but this week is set up for the national championship at 7,574 yards, which makes it the second-longest layout in the 111-year history of the tournament.

The leaders at the USGA usually look at something very close to par as an acceptable winning score and the changes they made at Congressional show how hard it could be to get the number as low as that this week. In a move that goes against tradition, the USGA actually added a stroke to par, turning the sixth hole from a 490-yard par-4 — of which there are already plenty on this course — into a reachable, 555-yard par-5, albeit with tighter fairways and a green designed to reject pushed shots into a lake on the right side.

“A well-executed shot will make it to that putting green,” USGA vice president Tom O’Toole said. “A poorly executed shot will not. It’s a primary example of risk-reward. Risk: bogey or double bogey by flirting with the water hazard. The reward: a two-putt birdie or a putt at eagle for 3.”

After that, though, it’s hard to find a lot of places to make birdie. Congressional doesn’t offer any drivable par-4s, a growingly popular USGA feature that, for instance, turned the 320-yard fourth hole at Pebble Beach last year and the downhill, 330-yard sixth at Winged Foot in 2006, into must-watch events.

The par-3s are all either long, or uphill, or over water, or some combination of all that. The par-3 10th is generating some talk this year; it used to be the 18th hole, but closing on a par-3 in 1997 turned out to be a bust, emphasized when Colin Montgomerie, in the running along with Els, waited more than 10 minutes to putt on No. 17 for fear the noise on the adjacent 18th would disrupt him.

“The average guy can’t play that hole,” Mickelson said in criticizing the design. “He can’t carry that water and get it stopped on that green. So when I play that hole, 3 is a great score.”