Rahm wrapped up his 10th professional victory with a magical shot that would have made his idol proud – although the drama was not done yet.

Starting the final round with a four-shot advantage, Rahm built an eight-shot lead at the turn but was only three shots clear with three holes to play at Muirfield Village.

In trouble behind the green on the par-3 16th, with Ryan Palmer eyeing a 12-foot birdie putt from the fringe, Rahm perfectly hit a flop shot from deep grass.

The ball landed on the fringe, ran toward the hole and dropped in for birdie as the fiery Spaniard let out a ferocious fist pump.

The only issue was the score.

Replays of Rahm's chip appeared to show the ball moved ever so slightly when he placed his lob wedge behind it as he surveyed the shot.

PGA Tour officials reviewed the incident and post-round issued him a two-shot penalty.

Rahm was surprised when it was mentioned to him after he finished and said he didn't realise anything was wrong.

"It doesn't take anything from the shot," he said.

"It's not going to take anything away from today."

Rahm closed with a three-over 75 to finish at nine-under 279 – a three-shot victory over Palmer (74).

Rahm chipped in at the par-3 16th hole. PHOTO: Andy Lyons/Getty Images.

A fourth PGA Tour title moved Rahm ahead of Rory McIlroy, whose 78 on Sunday left him a share of 32nd and 13 shots off the pace.

Rahm is the 24th player to be No.1.

Ballesteros spent 61 weeks at the top from 1986 to 1989.

England's Matthew Fitzpatrick had a 68 for the low score of the final day to finish third at five-under.

Queenslander Jason Day had another encouraging week, closing with a 73 for a three-way share of fourth at four-under.

The former World No.1 said after the third round his troublesome back was feeling dodgy and was looking forward to a week off.

Day has played six weeks in a row since the season resumed with an aim to improve his world ranking, which was 58th before the Memorial.

He is expected to play in the WGC-St Jude Invitational from July 30-August 2 before seeking a second US PGA Championship title when the major is hosted at the TPC Harding Park course in San Francisco the following week.

Tiger Woods, in his first competition since February, shot 76 and tied for 40th.

As is tradition, tournament host Jack Nicklaus was on hand behind the 18th green to greet the event winner – this time with a fist-bump for Rahm.

Nicklaus revealed earlier on Sunday that he and wife Barbara had tested positive for the coronavirus in March, and they have since tested positive for the antibodies.