It's Athens all over again. Time trials will be used to determine who swims the critical freestyle leg for South Africa in the men's 4x100m medley relay at the Rio Olympics next month, says Doug Erasmus, one of the contenders.Butterfly king Chad Le Clos and breaststroke star Cameron van der Burgh will spearhead the foursome, which was bolstered with the emergence earlier this year of US-based backstroker Christopher Reid.There's gold in them hills, it seems, until you mine the freestyle. If only SA had depth like when the 4x100m freestyle relay fleet torpedoed the world's best to triumph at Athens 2004.That relay lineup was decided by time trials a few days before the race, with hopefuls swimming alone, one by one. My goal there would be just to swim as fast as I possibly can, whether it's a 48.5 or a 47.9, just to give everything I've got Lyndon Ferns and Darian Townsend posted the best times ahead of Karl Thaning and Eugene Botes.Townsend, the slowest and youngest of the four, was well cushioned in the third leg of that relay, led off by Roland Schoeman and taken safely home by Ryk Neethling.But there's no place to hide for the freestyler in Rio.He is condemned to the final leg of the medley relay, which starts with backstroke followed by breaststroke and butterfly.SA has the potential to be among the top three, possibly even in the lead, at the last changeover.And when the South African freestyler dives in, several of the fastest swimmers on the planet will try to hunt him down.This is the glory - or hell - for which SA's freestylers are vying.Erasmus, in Pretoria this week during a brief trip home between training camps abroad, didn't know yet when the time trials would be held."The head coach will tell us, 'okay, we're going to do a time trial on this day', and anybody who is willing to do a time trial can rock up and race."Team management has previously said head coach Graham Hill would select the freestyler based on performances in training or even at the Games.The medley relay is the final race of the Olympic gala.Erasmus is the country's fastest available freestyler so far this year based on his 49.54sec personal best from the Olympic trials in Durban in April.World No1 is Australian Cameron McEvoy on 47.04, and sandwiched between him and Erasmus are 129 swimmers from 34 countries, including all-rounder Le Clos.Of the eight fastest medley relay teams over the past two years, Germany has the slowest freestyler, Damian Wierling, who went 48.54 at his national champs this year - still one second quicker than Erasmus.He said SA would need a 48-low in the freestyle leg to secure a medal, but was unfazed by the magnitude of the challenge."You hear about guys who pull out ridiculous times purely because of the environment, the atmosphere," he said, referring to the herculean effort by Jason Lezak at Beijing 2008 to overhaul France and clinch gold for the US in the 4x100m freestyle.Relay legs are about 0.5sec faster than individual times because of the flying start. The relay is in everybody's heads, everybody wants to have a shot ... this relay is medal potential Erasmus's rivals for the freestyle leg are likely to include Myles Brown, who went 49.59 in Monaco last month, Calvyn Justus and US-based Brad Tandy.Erasmus and Tandy qualified for Rio in the 50m freestyle."Quite frankly I have been thinking about [the relay] more than my 50 event," said Erasmus, 26."I have pictured myself, with the team together, that excitement, the adrenaline rush ..."My goal there would be just to swim as fast as I possibly can, whether it's a 48.5 or a 47.9, just to give everything I've got so I can't be disappointed with myself," he said.Erasmus jetted off to Fort Lauderdale, Florida, on Thursday night to rejoin the SA squad for their final pre-Rio tune-up."The relay is in everybody's heads," he added. "Everybody wants to have a shot ... This relay is medal potential."..