Cape Town - Cameron van der Burgh and Chad le Clos both failed to take to the starting blocks for their first assignments at the FINA World Championships in Budapest.
On Sunday, Van der Burgh pulled out of the 100m breaststroke heats, while Le Clos did not start in the men's 200m freestyle on Monday.
This leaves just the 50m breaststroke on Van der Burgh's schedule - an event in which he has won a medal at the last five World Championships, including two overall victories.
Van der Burgh has said his prime focus will be on the 50m breaststroke‚ which begins on Tuesday.
However, this decision could prove costly for the 2012 Olympic gold medallist.
According to the Times Live website, Van der Burgh could reportedly receive some financial backlash from SASCOC for his decision since the 100m breaststroke is an Olympic event, while the 50m is not.
Le Clos, South Africa's most decorated Olympic swimmer, was a surprise no-show in the 200m freestyle heats on Monday.
Le Clos won silver in the 200m freestyle at the Rio Olympics in 2016.
The final of the 200m freestyle would not have conflicted with his other races, which include the 100m and 200m butterfly later.
There were unconfirmed reports that Le Clos was feeling unwell, but remained unconfirmed at time of publication.