* Masters starts in bright and windy conditions
* World number one Johnson hopeful of recovering from injury
* Belgian Pieters leads on three under par
* Tributes to Arnold Palmer at sombre opening ceremony (Adds later details)
By Ed Osmond
AUGUSTA, Georgia, April 6 (Reuters) - The U.S. Masters started in bright and blustery conditions on Thursday with the fitness of world number one Dustin Johnson the major talking point around Augusta National.
Johnson, the American favourite to win the title after victories in his last three tournaments, sustained a back injury in a freak accident on Wednesday and was due to begin his first round in the final group out at 0203 PM local time (1803 GMT).
Johnson's trainer said he was progressing well and was cautiously optimistic about being able to tee off with compatriots Bubba Watson and Jimmy Walker.
Belgian Thomas Pieters set the early pace on three under par after seven holes, American Rickie Fowler made two early birdies and three-times Masters champion Phil Mickelson eagled the second to move on to a congested leaderboard.
Most players, however, found scoring difficult in the swirling winds.
Former Masters champions Jack Nicklaus and Gary Player struck the ceremonial opening tee shots to get the 81st edition of the year's first major off to a sombre start as they honoured Arnold Palmer, who died in September at the age of 87.
Thousands of golf fans wearing commemorative badges confirming their membership of Arnie's Army stood to attention during a poignant silence broken only by the sound of a chilled wind rustling through the trees.
Augusta National chairman Billy Payne addressed the crowds before Nicklaus and Player hit their drives without their long-time friend and rival at their side.
"Welcome to the 2017 Masters. It is a wonderful, but in one respect a difficult day," Payne said. "For the first time in many many decades, someone is obviously missing from the first tee.
"The almost unbearable sadness that we all feel by the passing of Arnold Palmer is only surpassed by the love and affection for him."
The bright weather was a relief for organisers, who were forced to call off the Masters Par 3 contest on Wednesday for the first time ever as heavy rain and storms buffeted the course.
England's Danny Willett will begin the defence of his title at 1224 PM alongside American Matt Kuchar and Australian amateur Curtis Luck.
World number two Rory McIlroy of Northern Ireland is among the late starters in a group with Japan's Hideto Tanihara and Spaniard Jon Rahm.
(Editing by Mark Heinrich, Neil Robinson)