By Mark Lamport-Stokes
AUGUSTA, Georgia (Reuters) - Jordan Spieth's love affair with Augusta National continued on Thursday as the reigning Masters champion fired a flawless six-under-par 66 to seize an early three-shot lead in the opening round.
The American world number two, bidding to become only the fourth player to claim back-to-back Masters victories, took advantage of relatively calm morning conditions to storm to the top of the leaderboard.
Shaking off a run of inconsistent form in recent weeks on the PGA Tour, Spieth sank a six-footer at the third, a 13-footer at the sixth and a four-footer at the eighth to reach the turn in three-under 33.
He then picked further shots at the 10th, 13th and 18th, where he rolled in a six-foot putt before pumping his fist in celebration, to finish three ahead of playing competitor Paul Casey of England in the year's opening major championship.
Also at three-under on an increasingly blustery day at Augusta National were England's Justin Rose, twice Masters champion Bubba Watson, pre-tournament favorite Jason Day and Shane Lowry.
Rose had completed 14 holes, American left-hander Watson eight, Australian Day seven and Irishman Lowry four.
Spieth won the PGA Tour's Hyundai Tournament of Champions in January, but struggled to string together four good rounds in his next five strokeplay starts before returning this week to the welcome surroundings of Augusta National.
He tied for second on his Masters debut in 2014, then last year stunned the golf world as he completed a wire-to-wire victory by four shots, matching Tiger Woods' tournament record low of 18-under 270 for 72 holes.
While Spieth flourished in Thursday's opening round, former world number one Ernie Els made a nightmare start as he seven-putted from just two feet at the par-four first to run up a mind-boggling 10.
It was the worst ever Masters score on that hole by two shots and left South African Els, who has struggled badly with his short putting for much of the past 12 months, shaking his head in disbelief.
Among the other early starters, England's former world number one Lee Westwood carded a 71 to finish level with Americans Charley Hoffman and Kevin Streelman.
"It's tough out there," Westwood, who is still seeking his first major title, said of the swirling winds at Augusta. "Very tricky.
"The flags, considering that there was going to be wind, they weren't by any means easy, so I'm delighted to be under par for the most part."
An overnight thunderstorm had made the slick greens at Augusta a little more receptive, though strong gusts of up to 35 mph (56 kph) were forecast for the afternoon, posing problems for late starters such as Day and Rory McIlroy.
(Editing by Larry Fine)