Joint-sixth starting out in the $6.5m Nedbank Golf Challenge at Sun City, Knox suffered his first off day since winning the WGC-HSBC Champions in Shanghai last month.
The 30-year-old slumped to a four-over-par 76 at the Gary Player Country Club to slip to four-over, leaving him sitting joint-22nd on one-over in the 30-man field.
The tone was set by three dropped shots in a row from the third and, with a double-bogey 6 at the eighth thrown in as well, Knox was out in 41.
Following a lengthy delay due to lightning, he dropped another shot at the 12th before staging a strong finish with two birdies in the last three holes.
The late flourish saw Knox finish the day ahead of Matt Fitzpatrick, who learned during the weather delay that he’d been pipped by Byeong Hun in the battle for 2015 European Tour Rookie of the Year.
Fitzpatrick’s British Masters win at Woburn in October was one of ten top-10 finishes for the 21-year-old Yorkshireman.
But a voting panel decided that An’s six-shot success in the BMW PGA Championship at Wentworth, coupled with the fact he finished five spots ahead of Fitzpatrick in the Race to Dubai, should see him become the first Korean to claim the Sir Henry Cotton Award.
An’s breakthrough 2015 season also yielded another prestigious title as the Challenge Tour Graduate of the Year, having used the second-tier circuit - including an appearance at Macdonald Spey Valley in Aviemore for the Scottish Hydro Challenge - as a step up to the main Tour.
“It’s a once-in-a-lifetime achievement,” he said. “I worked very hard for this and played great last season. There were a lot of other good rookie players, so to win the award is very special.
“The race went down to the final day of the final event – even the last hole. It was so close and I had no idea who was going to get it.
“I’ve seen the other names who have won this award over the years and I’ve joined a list of great players. It’s great to be part of that history. I’m the first Asian to win it and hopefully it will help bring more Asian players to play on the European Tour.”
Henrik Stenson, the world No 7, recovered from three bogeys in a row on the front nine to hold the halfway lead at Sun City.
The Swede stormed home in five-under for a 67 and an 11-under-par total, giving him a one-shot lead over South African Jaco Van Zyl (68).
Glasgow-born Yates, meanwhile, made a big leap up the leaderboard in the Ho Tram Open, an Asian Tour event being played at The Bluffs in Vietnam.
The 45-year-old, who is based in Thailand, posted a five-under-par 66 to leap from joint-33rd into a share of 17th on three-under 139.
Yates, a two-time Asian Tour winner, stormed to the turn in 30 after birdies at the first, fourth, fifth, eighth and ninth.
He picked up another shot at the tenth before mixing two birdies with two bogeys over the closing eight holes.
It was the joint-best effort of the day before play was suspended due to darkness following a delay caused by high winds.
Yates was sitting seven off the clubhouse lead, held by Lin Wen-tang of Chinese Taipei after he carded a 67 in the gusty conditions to sit two shots clear of American David Lipsky, who still had seven holes of his second round to play.
In the Australian PGA Championship on the Gold Coast, improved second-round performances were unable to prevent Scott Jamieson and Paul Shields from making early exits.
Jamieson’s 74 for a nine-over 153 total left him three shots below the cut mark while Shields was four shots further back after a 75.
Leading by one from a six-strong chasing pack at the RACV Royal Pines Resort is Swede David Lingmerth, who is making his first start as an affiliate member of The European Tour.
Elsewhere, Clydeway Golf’s Graham Fox matched the best round of the day in the second round of the Beko Classic at Montgomerie Maxx Royal in Belek, Turkey.
The PGA Cup player bounced back brilliantly from his opening 80 with a four-under-par 68 that contained eight birdies.
It lifted Fox into joint-14th on four-over, 10 shots behind joint-leaders David Howell - the Englishman was other player to post a 68 - and Swede Pontus Widegren (69).
Raymond Russell, the former European Tour winner from Prestonpans, and West Linton club pro Gareth Wright both carded 76s to slip to joint-11th and tied for 16th respectively.
On the women’s front, Catriona Matthew and her Ladies European Tour team-mates finished the opening day of The Queens, a new team event, lying in third position in Japan.
Reunited with one of her Solheim Cup playing partners from this year’s match in Germany, Matthew and Karine Icher from France finished all square against Korean LPGA pair Sung Hyun Park and Bo-Mee Lee in the opening fourballs.
However, the LPGA of Japan side finished the first day’s action at Miyoshi Country Club on 12 points, followed by the Korean LPGA on seven, the LET on four with the Australian LPG bringing up the rear after a fruitless day.
In Florida, Kylie Walker was making one of the big moves on day three of the LPGA Tour Qualifying School. The 29-year-old Glaswegian had moved into the top 15 after covering her first 11 holes in four-under-par on the Jones Course at LPGA International at Daytona Beach.