Cape Town - Chad Le Clos has laid one hand on the men's crown, even though he suffered a setback on the second day of the FINA Swimming World Cup in Tokyo on Wednesday.
Le Clos set a breakneck pace in the 200m butterfly to touch home in 1:50.71.
He then had to play second fiddle to Australia's Cameron McEvoy in the 200m freestyle, taking silver in a time of 1:43.56 with McEvoy 0.19 seconds ahead.
"I really wanted to go for it tonight, but it felt weird. Cameron attacked and good luck to him. I'd love to win them all, but that was a good race," said Le Clos, as quoted by fina.org website.
"I've got to do a bit better now in Singapore and be a bit more consistent in that middle 75 - it's a bit of a grey area. It's the toughest night in a while, but it's been a good two days."
On the opening day of the cluster in Tokyo, the South African bagged a gold and silver medal.
After the completion of the penultimate cluster, Le Clos has extended his lead in the men's rankings on 402 points with his nearest competitor Vladimir Morozov of Russia on 273 points.
The Rio silver medallist has won the Swimming World Cup three times - in 2011, 2013 and 2014 - and could become the first man to win four World Cup Series titles.
The Swimming World Cup overall series finale gets underway in Singapore on Saturday and Sunday.