But Stenson immediately responded with a birdie before a weak chip on the next resulted in Coetzee losing a shot.
A hat-trick of consecutive gains for Martin Kaymer moved him to a tie for third as he bids to produce a dramatic finish akin to his Ryder Cup winning putt this season.
Last year’s Masters Tournament champion Charl Schwartzel also made inroads after carding two double bogeys and a pair of bogeys yesterday as he joined Kaymer, Magnus Carlsson and Thomas Aiken on 11 under par.
Tommy Fleetwood turned in 34, in a tie for eighth, knowing he must place within the top 27 to ensure his playing privileges for next season.
Earlier, Hennie Otto had set a new course record at the Serengeti Golf & Wildlife Estate on what is likely to be his final day as the reigning champion.
The 2011 victor had failed to replicate last season’s form this time out as he barely made the cut before dropping a shot on four successive holes in yesterday’s 75.
But the South African produced a scintillating 62 this morning to ensure he finished on eight under par for the tournament.