Jordan Spieth fell foul of a crackdown on slow play as a "masterclass" from Rory McIlroy ensured the world No 3 won their first duel of the year at the Abu Dhabi HSBC Championship.

With the focus well and truly on these two global superstars, it was going to take something special to grab a chunk of the limelight and Bryson DeChambeau, the US Amateur champion and Walker Cup player, certainly did that as he surged to the head of field with an eight-under 64 to lead by one from Sweden's Henrik Stenson.

McIlroy had insisted he was not concerned about laying down a marker to Spieth after being drawn with the Masters and US Open champion, but the four-time major winner certainly made an impression with an opening 66.

"It was a masterclass, the Rory that I have seen win major championships," Spieth said after a birdie on the last ensured he finished with a 68.

McIlroy did not touch a club for eight weeks after winning the DP World Tour Championship in November, but the only evidence of rust came with two three-putt bogeys, each of which he immediately followed with a brace of birdies.

"It was a great way to start the year," said McIlroy, who has finished second in Abu Dhabi four times in the last five years. "I felt in practice last week I was swinging well and I came back mentally fresh and excited to play again. I could not be happier."

Spieth, who came into the event on the back of an eight-shot victory on the PGA Tour in Hawaii, admitted his driving was "short and crooked" for most of the day, but was more concerned with receiving a "monitoring penalty" on the penultimate hole.

"It was a bit odd," said the world No 1, who will be fined £2,000 if he transgresses again. "I got a bad time on my putt on the eighth when they took us off the clock on that green and the guys behind us hadn't even reached the fairway on a par five.

"I understand that if you are being timed and you are taking longer than the allotted time, you get a bad time. I understand the rule but it doesn't make a whole lot of sense when our group had caught up."

McIlroy sympathised with Spieth and felt officials should use "common sense" as they were not out of position, but that cut little ice with European Tour chief referee John Paramor.

"Pace of play on the European Tour is measured by whether a group keeps to the starting interval between groups, rather than if they are on the same hole, as it is in America," Paramor said.

Early leader DeChambeau became the fifth player after Jack Nicklaus, Phil Mickelson, Tiger Woods and Ryan Moore to win the NCAA and US Amateur titles in the same season last year, but has also made headlines for his unique approach to the game.

The physics graduate describes himself as a "golf scientist" and has modified his irons so that they are all the length of a six iron, while he uses water and Epsom salts to establish which of his golf balls are slightly flawed (he says about four per dozen) so they can be discarded.

"It was quite incredible," DeChambeau said of his round, which contained seven birdies, an eagle and one bogey. "I had no expectations and was just able to freewheel a little bit and that allows me to do my best."

Russell Knox and Scott Jamieson were the pick of the Scots with two-under 70s on a day of mixed fortunes for the tartan contingent. Paul Lawrie, the former Open champion, struggled to a 77 while Stephen Gallacher, a two-time winner in nearby Dubai in recent seasons, sagged to an 81 as his 2016 campaign got off to the worst possible start.