Dustin Johnson justified his ranking as world-number-one with a victory, in his first start since reaching the peak, at the WGC-Mexico Championship.

A final round 68 moved the 32-year-old past the day-beginning leader Justin Thomas and held off strong challenges from Tommy Fleetwood, Jon Rahm and Ross Fisher to earn him his second consecutive win at the first World Golf Championship at Chapultepec Club de Golf.

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On his first start since a rib injury that had sidelined him since mid-January, Rory McIlroy made a promising return to tour golf, most notably with a Friday 65, but was unable to capitalise on Sunday having began just two shots behind the leading Thomas – eventually falling back to tied seventh.

23-year-old Thomas began the day at 12-under-par with a one shot lead over Johnson; but after a rocky three-over front nine for the 23-year-old, and an electric 31 out for Johnson, Thomas slipped to tied fourth and Johnson entered the back nine with a four-shot lead over the climbing Thomas Pieters.

A 360 degree lip-out on the 11th robbed Fleetwood of an eagle although a birdie on the 12th applied a bit of pressure to the leader and he joined Pieters at 11-under-par who, after a promising start of three birdies on the opening four, struggled to move from 11-under.

Rahm, a group in-front of the leader, moved into contention as the main threat to Johnson with an eagle on the 11th to make the latter aware of his presence; nevertheless, still three shots back.

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A birdie on the 12th would have put Rahm within two of the leader but the 22-year-old was denied by a lip-out. However, a missed close putt on the same hole from Johnson gave him his first bogey of the round and it followed immediately with another on the 13th to drop him back to 13-under, cutting his lead over Rahm to just one.

Fisher recorded nine final round birdies to get within two shots but perhaps left his charge a bit too late. Meanwhile, Fleetwood registered a 15th hole birdie to get to within one shot of leading pair.

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Rahm, full of reignited hope, responded to Johnson’s stutter immediately with an off-the-green putt for birdie on the par four 14th for a share of the lead. The par fifth 15 was the scene for him to then take the outright lead for the first time with a birdie; before Johnson matched and joined the rookie at 15-under-par and two shots clear of the pack.

Six-foot par saves for Rahm slipped by right on the 16th and left on the 17th to knock the youngster down to tied second, soon tied third after Fleetwood would sink a 40-foot birdie putt on the 18th, and open the door for Johnson to close out par-par for his fourth World Golf Championship title.

The fourth WGC victory for Johnson puts him outright second in the list of most successful WGC players of all time; the American sits behind Tiger Woods who has 18 (eighteen) victories of his own. In such a high calibre event, Johnson’s win will solidify his position at the top of the world rankings significantly with major season just around the corner.