The duo carded three-under-par 69s on a revamped Leopard Creek course to sit joint fourth, three shots behind Oliver Bekker as the South African came in late on to edge ahead of Australian Dimitrios Papadatos.
On an encouraging day for the Scottish contingent, on-form Bob MacIntyre fired a 70, as did Marc Warren after he recovered from an ugly eight at the second hole to finish with a hat-trick of birdies, while Scott Jamieson also broke par with his 71.
Drysdale, who started the 2019 campaign by finishing fifth in the Honma Hong Kong Open last month, was only able to play one round in the South Africa Open at Randpark in Johannesburg.
The 43-year-old from Cockburnspath trapped his arm in an electric gate at the house he was staying in, bruising it in the process and, though nothing serious, he was unable to continue after the opening round.
Not hitting shots for a few days seemed to have been exactly what was needed, though, as Drysdale, pictured below, returned to action by carding five birdies, including four on his back nine after starting on the tenth.
“I played nicely today in tricking conditions,” he said before saying of his injury: “It was really just bruising and three days of rest last weekend did the trick.”
Johnston, one of the four new Scottish card holders on the circuit this season, had a rollercoaster round. The 25-year-old from Dumfries was two-under after two before finding himself one-over after seven but then reeled off four birdies in seven holes, including three in a row from the 13th.
Taking up where he left off when shining in the company of Ernie Els in the final two rounds to finish joint 15th in the South Africa Open, MacIntyre came home in two under. “It could have been better or worse, but I will take it,” said the 22-year-old from Oban.
Warren opened with a birdie before running up his triple-bogey eight but the 37-year-old Glaswegian showed guts to bounce back with six birdies, including that late salvo.
David Law was three-under after four holes but had to settle for a 72, which was matched by Doug McGuigan, while Grant Forrest was four-over at the turn before salvaging a 74.
On a day when Bekker carded six birdies to set the pace, Aberdeen Standard Investments Scottish Open champion Brandon Stone is lurking ominously alongside Drysdale, while Louis Oosthuizen, the South Africa Open winner, is also handily placed on 71.