World No 1 and US Open champion Dustin Johnson had been a heavy favourite to take his first Masters title but his odds lengthened after he injured his back falling down the stairs at his rented Augusta home.
Rory McIlroy is Britain's best chance of success – the Northern Irish golfer is ranked No 2 in the world and has finished in the top 10 for the last three years at Augusta.
Masters 2017 odds: Who are the 15 favourites to triumph at Augusta?
Wed, April 5, 2017
Which man is favourite to triumph at Augusta? Odds provided by Paddy Power
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Click to reveal the top 15 favourites to win the Masters 2017
Live Masters updates from Augusta
5.40pm BST: We have a clubhouse leader – but given that he is the first man in, it doesn't mean much.
Russell Henley has made it round in 71 to sign for a one-under-par score and given the wind has been quite whippy and should get stronger, he will be very pleased.
Pieters is still going strong as well. He sinks another birdie putt to go five under through 10.
5.10pm BST: Mickelson on the move but Pieters responds! It may only be Thursday afternoon but we've got two men battling at the top of the leaderboard already.
Mickelson birdies the par-3 fourth to join the Belgian at the top before he gets a shot at 8 and goes to -4. The American has dropped back to two under now though with a mistake at the fifth.
4.40pm BST: We hear the first Augusta roar of the week and it was only ever going to be for Phil Mickelson.
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There wouldn't be a more popular winner in Georgia this week than the 46-year-old American who has three Green Jackets already and 15 (FIFTEEN) finishes in the top 10.
Mickelson makes eagle at two for a strong early start.
4.25pm BST: Martin Kaymer is out on course and the big German is already putting his fans through the ringer with a bogey at the first and an eagle at the second.
The 2014 US Open champion has never finished in the top 30 at Augusta and missed five cuts in his nine appearances.
4.10pm BST: Rickie Fowler is hoping to clash his final-day orange outfit with the Green Jack on Sunday evening and he's made a good start with birdies at two and three.
Pieters is also making a move and the 25-year-old makes his third birdie of the day at the par-4 fifth hole.
3.40pm BST: The English have recovered some early pride after Gergor's problems. Andy Sullivan is wearing some outrageous shoes and picks up an early birdie.
His Ryder Cup team-mate Thomas Pieters of Belgium is also under par. His big-hitting game could suit the damp course this week
3.20pm BST: Sandy Lyle is one shot off the lead. Yes that Sandy Lyle. The 1988 Masters champion birdies the third and moves to one shot behind current leaders Scott Piercy and JB Holmes.
Lyle is 59 years old but did finish 20th at Augusta as recently as 2009. That said, it's probably worth enjoying his time at the top now as it's unlikely to last.
3pm BST: There is an update on Dustin Johnson after he fell down his stairs last night. The world No 1 has arrived on the range at Augusta, four hours ahead of his tee time, and is expected to play.
2pm BST: Russell Henley was the last man to qualify for the tournament, winning the Houston Open last weekend.
Kevin Chappell was the first man to get to two under par in the early stages of the Masters
He has the honour of playing in the leading group with Daniel Summerhays and both make birdies at the second hole to take the early lead.
Players will continue to go off every 11 minutes until Bubba Watson, Dustin Johnson and Jimmy Walker hit the course as the last group at 7.03pm BST.
Meanwhile, Kevin Chappell sinks another birdie putt at the second and leads the Masters on his own from Henley.
2.40pm BST: Trouble for the first Englishman out on course. Scott Gregory is the British Amateur champion and makes his debut at Augusta this year but it has not started well.
The 22-year-old from Hampshire is over the back of the first and takes five shots to get up and down, carding a triple bogey on his first ever Masters hole. He then goes on to bogey the second as well. Ouch.
Masters legend Arnold Palmer passed away last year but his Green Jacket was present
1.30pm BST: Gary Player and Jack Nicklaus, both former Masters champions and honorary starters for the 2017 tournament, hit the ceremonial opening tee shots down the first hole.
Last year, the pair had done so with Augusta legend Arnold Palmer watching from his wheelchair. Palmer passed away in September last year at the age of 87.
Both Player and Nicklaus gestured to the heavens after hitting their shots and embraced, wiping away tears from their eyes.