The South African was a picture of consistency down the stretch as those around him faltered.
The Pole takes a one-shot lead into the final round at Leopard Creek.
Scotland’s Scott Jamieson lies a shot behind following a 66.
Casey opted out of the inaugural event in 2019, citing concerns over the country’s human rights record.
Hansen trailed by three shots with nine holes to play but won by two strokes.
He won his second major on Sunday.
The 12th hole played a key part in his memorable Augusta victory last April but it was not to be a happy hunting ground again.
Dustin Johnson has held the lead of a major championship four times previously – and won none.
The world number one is in a commanding position.
Five players were sharing the halfway lead at Augusta National.
Australia’s Cameron Smith and Mexico’s Abraham Ancer are also nine under par.
The English trio of Tommy Fleetwood, Justin Rose and 2016 winner Danny Willett are on seven under.
Rory McIlroy battles back and Dustin Johnson is part of a four-way tie for the lead.
McIlroy was level par when play in the delayed first round resumed on Friday, but covered the back nine in three over to fall 10 shots off the lead.
Casey fired an eagle and five birdies in a flawless 65.
Woods returned a bogey-free 68.
Bryson DeChambeau and Tiger Woods are hoping to make an early impression at Augusta National.
The American is bidding to make it back-to-back major titles.
Woods claimed his 15th major title more than 11 years after number 14 at the 2008 US Open.
The Spaniard will miss a major championship for the first time since 1999.
The long-hitting US Open champion is favourite to make it back-to-back major titles.
The Scot birdied four of his last six holes at Aphrodite Hills to card a seven-under-par 64.
The 44-year-old had to wait 3,954 days between his 14th and 15th major titles.
Shortly after Nicklaus posted his statement, Trump thanked the 80-year-old for his support.
McIlroy would become only the sixth player to complete golf’s ‘Grand Slam’ of all four modern majors by winning the rescheduled 2020 Masters at Augusta next month.
The Englishman had just one European Tour top 10 in four seasons when he arrived at Chervo Golf Club.
The 44-year-old is happy with his game as Masters season begins in earnest.
The Spaniard Otaegui now has a professional victory in three different formats of the game.