MEXICO CITY (AP) Dustin Johnson thought he had the altitude figured out.
He made four birdies on the back nine at Chapultepec Golf Club and was 2-under par at the turn, right about where he was expected to be in his debut as the No. 1 player in the world at the Mexico Championship. The first hole was 316 yards and Johnson felt a light breeze in his face, so he opted for a cut 3-wood.
Except that it didn't cut from left-to-right. And from that distance, Johnson could still see a marshal at the back of the green turn and start looking in the thick hedges behind the green. ''I'm going to hit a provisional,'' he said.
The hole didn't end well.
Johnson had to get on his stomach to see the ball in the hedges, and he still had hopes that it was just inside the out-of-bounds stakes. No such luck. He had to play his provisional - a 2-iron about pin-high into a bunker - blasted out to 3 feet and missed the putt to make double bogey.
That hole epitomized why Chapultepec - and the Mexico Championship - held its own Thursday against the best in the world.
Even at nearly 7,800 feet of altitude that sent tee shots soaring - Roberto Castro hit one drive 407 yards - players still had a difficult time making sure they were hitting it the right distance. And while the course played much shorter, the greens have just enough slope and undulation that making putts was never easy.
The result was a six-way tie for the lead at just 4-under 67.
Among the leaders were Phil Mickelson and Lee Westwood, two of the four players who were at Valderrama in 1999 when this World Golf Championship began. Mickelson made birdie on both par 5s on the back nine, closed with another birdie and that was all it took to tie for the lead.
For those who thought the best players would eat up this golf course, Mickelson didn't see it that way.
''You really aren't able to overpower the course because of how tight it is,'' He said. ''That makes the precision with the irons more important. The greens are very difficult to putt. They don't look as difficult as I think they are.''
Westwood sure didn't see eight birdies out there, but that's what he had with a tee shot into 4 feet for birdie on the par-3 seventh, his 16th of the round. That put him at 6 under, and even a bogey-bogey finish didn't bother him.
''The distance control up here out of the rough at this altitude to some of these greens is very challenging,'' Westwood said. ''So with a little bit of heat as well, the ball's going ridiculous distances. So it's not easy out there to get the ball close, and if you do start to get it on the green but a long way from the flag, it's not the easiest two-putt because these greens are quite tricky.''
The others at 67 were PGA champion Jimmy Walker, Jon Rahm of Spain, Ross Fisher of England and Ryan Moore. All had tales of getting the distance right and trying to make putts. Rory McIlroy was in the large group at 68. McIlroy was playing for the first time since Jan. 15 because of a hairline fracture of his rib. A bad stomach bothered him a lot more, but he made it through the day.
Only three players managed to avoid a bogey - Sergio Garcia and Pat Perez at 68, and Rickie Fowler at 69.
Walker also reached 6 under with a wedge to 4 feet on the par-5 sixth. He didn't feel as though he missed a shot over the final three holes, yet he still managed to make a pair of bogeys.
With a 7-iron on the 235-yard seventh hole, Walker was posing until he saw it land about 10 feet behind the flag, take a hard hop and settle in the collar behind the green. That left him 50 feet from the flag, straight down the slope, except all putts are said to break toward the city, and the city was behind him. He left it 8 feet short, hit a good putt and watched it wiggle off to the left.
Then, his approach to the long par-4 eighth was just off to the right and when Walker reached his ball near the gallery, he knew he was in trouble. His pitch had to stop when it reached the green or it would roll some 30 feet away. It stopped a foot from the green, and he barely rapped it with his putter from 30 feet. It stopped next to the cup for another bogey.
''The couple bogeys I made, I felt like I didn't hit any bad shots,'' Walker said. ''Just a bad deal. But solid day.''
As for Johnson?
He wound up with a 70, and the double bogey turned out to be the least of his problems. He missed six putts from 6 feet or in, and he's not really sure why.
''That's how it goes,'' Johnson said.
He starts his second round Friday. Look for Johnson to hit a 2-iron on the first hole.