CARNOUSTIE, Scotland — The way golf has been going the last few years, it would be reasonable to see the name "Johnson" atop the leaderboard and assume it belonged to the No. 1 player in the world.

But not necessarily at the British Open.

Zach Johnson — not Dustin — already has his name on the claret jug. And the way he handled the rain Friday in his round of 4-under 67, he might have a chance to see it on that precious silver trophy again.

Johnson holed a 30-foot birdie putt on the 18th and had a one-shot lead over Tommy Fleetwood at the midway point of the second round. Fleetwood, the top player on the European Tour last year, put together the best round of the week at Carnoustie with a 65.

Rory McIlroy had another 69 and was two shots behind. Adam Hadwin, the only Canadian in the field, shot a 1-under on Friday to make the cut at +1.

Johnson was at 6-under 136, and had to wait to see if it would hold up. Kevin Kisner, the 18-hole leader, was among the late starters.

The light rain from overnight never let up. It wasn't enough to turn the colour of grass from brown to green, just enough to be a nuisance playing in rain gear, with towels hanging from the inside of umbrella to stay dry and putting surfaces that were slightly slower.

Johnson overcame a bogey on the opening hole with birdies on the third and fourth holes, and he never put himself under too much pressure the rest of the way.

Already a two-time major champion with titles at St. Andrews and Augusta National, the 42-year-old from Iowa now has made the cut 12 straight times in the British Open, a streak that began at Carnoustie in 2007. His low ball flight, grinding nature and good putting give him the right ingredients.

As for that other Johnson?

Dustin Johnson was headed toward being the first No. 1 player in the world to miss the cut at the Open since Luke Donald in 2011 at Royal St. George's. He appeared to keep it together with a tough par save from the bunker on No. 12, followed by two straight birdies. But he had another poor finish, closing bogey-double bogey for a 72 and is at 6-over 148 for 36 holes.

Even as Tiger Woods was piecing together a level round, and late starters like Kisner and Jordan Spieth were still on the course, the cut figured to be about 3-over, plus or minus one shot.

Zach Johnson and Dustin Johnson, one of golf's most powerful players, share nothing in common but a surname. That hasn't kept the casual fan from occasionally calling Zach Johnson by the wrong name.

"I certainly am not the No. 1 player in the world that ends in 'Johnson," he said. "I've been called Dustin many times. I doubt he's been called Zach that many times.

Zach Johnson has more than held his own. In the power era of golf, he is more of a pistol than a cannon. And yet he has still won 12 times on the PGA Tour, along with majors at the Masters and British Open.

Fleetwood and McIlroy were playing a few groups ahead of Johnson, and it was a race to see who would wind up on top for much of the late morning until Johnson made his birdie putt on the final hole.

Fleetwood shot 63 at Carnoustie last year in the Dunhill Links, but that was a European Tour event. In more difficult conditions, his 65 felt just as good, especially the birdie on the 18th that put him atop the leaderboard until Johnson finished.

McIlroy, meanwhile, was within one shot until a long three-putt from just off the 12th green. He gave another shot back on the 15th when he pulled his second shot toward the gallery, though he made enough birdies to stay within range.

"Under those conditions, I would have taken that score today going out," McIlroy said. "It wasn't that bad, but it was just damp enough and cold enough that the game plan that I was trying to adapt to be aggressive and hit driver a lot, I just couldn't do it. ... So a lot more irons off tees and a lot more conservative, but ended up being the same score."

Dustin Johnson wasn't alone in his struggle this week. The No. 2 player in the world, Justin Thomas, also was headed toward a weekend off. Thomas was 2 under for the tournament when it took him two shots to get out of a pot bunker in the sixth fairway and three putts from long range on the green, leading to double bogey. He then made double bogey on the next two holes and wound up with a 77 to finish at 4 over.