Ostrava - The majority of the South African contingent put up firm challenges on Tuesday night, but they ultimately struggled against world-class line-ups at the Golden Spike athletics meeting in Ostrava.
Sprinter Simon Magakwe and hurdler Wenda Theron finished fourth in their respective events, achieving the best South African performances of the evening, at the ninth leg of the IAAF World Challenge series.
Magakwe was again slow out the blocks but he charged through in the final 30 metres to snatch fourth place in the men's 100m dash in 10.19 seconds.
Harry Aikines-Aryeetey of Great Britain was given the same time in fifth place, while American Justin Gatlin coasted to victory in 9.86, the fastest time in the world this year.
Nel, meanwhile, went out hard over the first 200m and held on doggedly down the home straight to clock 55.53 seconds in the women's 400m hurdles race.
Nickiesha Wilson of Jamaica won a tight contest in 55.22.
Wouter le Roux finished fifth in the men's one-lap race over the barriers in 50.15 seconds, well behind Niall Flannery of Great Britain who produced a breakthrough performance to win in a personal best 48.80.
Middle-distance runner Caster Semenya found herself among the early front runners in the women's 800m event, after the pace setter withdrew injured, but the SA record holder faded badly on the second lap.
Semenya's poor form continued as she ended 14th, and last, in another pedestrian time of 2:03.91.
Winnie Nanyondo of Uganda grabbed a surprise victory in a national record 1:59.27.