But the Dumfries & County player said he felt sorry for compatriot Craig Ross after the defending champion had to concede in their all-Scottish second-round tie due to illness.
“It’s never nice to see a match end that way, especially against a good mate,” admitted Johnson, who was three up when the Kirkhill player called it a day on the seventh hole.
“I was up sick all last night and just felt weak and dizzy, as well as sweating a lot, this morning,” said Ross. “I tried to play but was just getting worse on the course.”
Johnston, who used an unexpected but welcome rest to then beat Swiss player Robert Foley 6&5 in the afternoon, is bidding to become the fifth Scot in the last seven years to claim the title.
“I feel my game is in good shape,” he said after setting up a quarter-final clash with Caylum Boon from Oubaai Golf Club. “I’m trying just to stay focused on each round as it comes, but it would be nice to keep the good run going and hopefully I’ll still be there come Friday afternoon.”
Elsewhere, former Walker Cup player Ewen Ferguson has started his first full season in the professional ranks with two top-20 finishes on the Alps Tour, backing up claiming eighth spot in the Ein Bay Open at Sokhna in Egypt by securing a share of 17th in the Rea Sea Little Venice Open at the same venue.
“I played nicely in both events and did everything very solid,” said the Bearsden player. “I knew that I would still be a little rusty, so didn’t get too frustrated with myself. I really enjoyed my golf and was excited to get out and compete.
“I didn’t play amazing, but it was another stepping stone and I look to keep moving foward and getting better and learning all the time. Hopefully I can push on from this.”