Amateur Bryson DeChambeau made a name for himself by taking a one-shot lead in the Abu Dhabi HSBC Golf Championship after a first round that saw Jordan Spieth warned for slow play as Rory McIlroy started the year in ominous fashion.
World number one Spieth and four-time major winner McIlroy were the centre of attention on Thursday in an all-star group that also included the flamboyant Rickie Fowler, but it was the Northern Irishman who laid down a marker.
McIlroy endured a frustrating 2015, failing to add to his tally of major victories and suffering an ankle injury playing football as Spieth claimed his first two major titles and took over at the top of the rankings.
World number three McIlroy said he was feeling "really refreshed" before teeing off at the Abu Dhabi Golf Club - where he has been runner-up four times - following a seven-week break and that was evident as he carded a six-under 66 to sit tied for third place with Branden Grace.
Spieth is two shots adrift of Race to Dubai champion McIlroy and also fell foul of new European Tour rules, having been issued with a monitoring penalty for the length of time it took him to take a putt at the eighth - his penultimate hole of the day.
While it was not one of Spieth's better days, his fellow American DeChambeau matched the lowest opening round by an amateur on the European Tour by carding an impressive 64.
The 22-year-old was only one under after seven holes, but made an eagle three at the eighth and reeled off another five birdies - and seven in total - to surge to the top of the leaderboard.
DeChambeau, playing in only his second European Tour event, holds a one-shot advantage over the experienced Henrik Stenson, who made eight birdies and is firmly in the hunt six weeks after undergoing knee surgery.
Grace matched McIlroy's 66 to put himself in the mix, while English duo Richard Bland and Andy Sullivan are a further shot back on five under.
McIlroy birdied his first two holes, but dropped shots at the 13th and 17th after starting on the back nine, while Frenchman Gregory Havret made a hole in one at the 15th, but was level par at the end of his final round.