Roland Schoeman, who earned three medals at the 2004 Athens Olympics, fell short in his attempt to qualify for the 50m freestyle event at the national swimming trials in Durban on Saturday.
The 35-year-old Schoeman, who was sixth at the 2012 London Games, clocked 22.75 to take third place in the final at the SA Aquatic Championships, nearly half a second shy of the required 22.27 standard.
He had also clocked 22.40 in the preliminary rounds.
The nation’s top swimmers needed to achieve the qualifying times at the trials to be considered for selection.
Meanwhile, in Germany, 44-year-old distance runner Hendrick Ramaala finished 49th at the Hamburg Marathon in 2:24:52.
Ramaala, taking part in his final 42km race before the April 30 qualifying deadline, had clocked 2:17:12 in Cape Town in September.
While he dipped under the 2:19:00 standard, a long list of his younger compatriots had run faster during the window period, with only three spots available for the men’s marathon team in Rio.
Schoeman and Ramaala had both hoped to become the first SA athletes to compete at five editions of the global multi-sport showpiece.