Casey learnt earlier this week that his American coach Peter Kostis, who also works as an on-course commentator, had been given the all-clear following his battle with cancer.
And after receiving some advice from Kostis following a second round of 75, Casey improved by 10 shots on Saturday to climb from three over par to four under and boost his chances of climbing into the world's top 64 in time for the WGC Accenture Match Play Championship in February.
The world number 88, who was three over par after two holes of his opening round, carded two bogeys and nine birdies, the last of which came on the 18th after his tee shot on the short par four ended up on the first tee.
"I'm really pleased with that because I struggled yesterday and sent a panic text to Peter," the 36-year-old said.
"He hadn't seen me on television because I was playing so badly I wouldn't have been on the coverage, but he said I always get too quick in the wind so slow it down.
"That obviously worked and I struck it beautifully today and holed a few good putts to keep the round going. After being three over for two holes on Thursday you wonder how bad it could get over 72 holes, but thankfully I've got it back into the red."
Speaking about Kostis, Casey joked: "The doctor gave him the all-clear and that's good because it means I don't have to be nice to him. He's got no excuses now.
"It's very good news, it couldn't be better. He spent a lot of time with me on the range over the winter and even though he had finished with chemo three or four weeks ago he was still tired. He desperately wants to get back to work and so do I, because he's driving me nuts when he's at the golf course every day!"
Meanwhile, Casey's Seve Trophy team-mate Tommy Fleetwood had moved into the outright lead on 10 under par, one shot ahead of local favourite and defending champion Louis Oosthuizen.
Fleetwood, a former Walker Cup player and 2011 Challenge Tour winner, birdied the third, fourth and ninth to be out in 34, while former Open champion Oosthuizen had carded five birdies and three bogeys in his first 12 holes.
Holland's Joost Luiten, who shared the overnight lead with Fleetwood and Oosthuizen after firing an albatross in his 67 on Friday, was a shot further back on eight under.
A three-putt bogey from Fleetwood on the 14th, coupled with a birdie from Oosthuizen on the 15th, saw the lead change hands, but it quickly changed back as Oosthuizen ran up a triple-bogey seven on the 16th following a wild drive.
That left Fleetwood in the lead on nine under, one ahead of Luiten and France's Victor Dubuisson, with Oosthuizen a further shot back.
Former champion Branden Grace had set the clubhouse target on seven under, with Welshman Jamie Donaldson on six under after a 68 as he warmed up for the defence of his Abu Dhabi Championship title next week.