• Johnson wins first competition as world No1 from Tommy Fleetwood • The 22-year-old Spaniard Rahm tied for third with Ross Fisher

For Dustin Johnson there were back-to-back wins, a fourth World Golf Championship and endorsement of his status as the No1 golfer in the world. For European golf there was further evidence of a new star in the form of Jon Rahm. During a Sunday afternoon spell on the outskirts of Mexico City the Spaniard threatened to make history by upstaging illustrious opposition.

Just 12 months ago Johnson was the nearly man. He was yet to claim a major championship and had not been ranked at the summit of the world rankings. Such a scenario was widely regarded as ludicrous, such was Johnson’s ability in comparison with those who had achieved more.

Johnson arrived at the WGC-Mexico Championship both as the US Open champion and, for the first time in competition, world No1. He departed on Sunday evening as outright second for career WGC victories, a closing round of 68 securing a 14-under-par aggregate and single-stroke success. Johnson even had the luxury of missing 16 putts from inside 10ft over four days. It is testimony to Rahm that Johnson had to win this tournament twice.

The American held a seemingly unassailable four-shot lead at the turn before surprisingly dropping strokes at the 12th and 13th. Rahm’s four-under-par run from the 11th tee to 15th green meant he shared, and very briefly held, the lead.

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Rahm faltered with bogeys on the 16th and 17th as Johnson picked up a shot at the 15th, giving the latter sufficient leeway – a wonderful Tommy Fleetwood putt aside – to cross the line in front. Rahm, 22, should have the consolation of a move up to No25 when the world rankings are published on Monday morning.

“I didn’t play great every day and still had a chance to win the tournament,” Rahm said. “I’m not going to play great every day but that’s where you want to be, producing respectable scores without your A-Game. That’s going to keep you going for a long time and I was just glad I could do that.

“This was my first chance here on this golf course, the first time I played this kind of event and to actually have a chance? It’s really nothing but positive.”

Although Rahm made the most serious charge at Johnson, he was far from the only European to shine. Ross Fisher’s 65, rounded off by three birdies in a row, should secure the Englishman a place in the WGC Match Play Championship and leaves him within touching distance of a Masters berth. He shared third with Rahm.

Fleetwood holed out from 38ft on the final green, securing second spot and meaning Johnson at least had to par his last two holes at worst. Fleetwood, who won in Abu Dhabi earlier this year, is in the form of his life.

Rory McIlroy will be grateful for the Mexico run. The Northern Irishman entered this event with low expectations after a seven-week break from play caused by injury, but had a mind-set shift when holding a two-shot lead at halfway. McIlroy regarded a share of seventh as disappointing but the broader picture relates to fitness and the buildup to the Masters.

“I was hoping to improve as the week went on,” McIlroy said. “That was obviously the plan; that’s the plan every week. I hit it pretty well every day but the course changed a little bit as the week went on and I didn’t quite adjust to it.

“First week back it’s OK but being two ahead going into the weekend, obviously I’m disappointed with the finish.”

Justin Thomas had started Sunday with the lead but soon displayed some of the old, damaging traits which have so far ensured talent is not rewarded by victories.

It was difficult for neutrals to root for Thomas as he dropped – and, in one case, threw – clubs while offering other examples of petulance. Thomas turned in 38, by which point the damage was done; he signed for a 72 and a tie for fifth with Thomas Pieters.

It was remarkable to think Lee Westwood was within a shot of the lead after four holes, given the capitulation which followed. The Englishman had two sevens on the way to a 78, which undermined excellence from earlier in the tournament. Westwood can take heart from the appearance of Augusta National, where he finished second in 2016, on golf’s horizon.

As far as Johnson is concerned, that first major of the year cannot come quickly enough.