Johan Cronje, South Africa's only medallist at the last world championships in Moscow in 2013, treats every race like a chess match. It doesn't matter whether it's the first round of the 1500m or the final, he uses the grey cells.The married father of one, who jets off to Beijing tomorrow ahead of the world championships that kick off on Saturday, studies his rivals, anticipates their strategies and then devises his own tactics.And for the final this year, he is predicting the kick will come sooner than last time, probably about 600m out, maybe earlier."That's what I have been training for, that's what I'm gambling on," Cronje, 33, said with a laugh from his Bloemfontein base this week."You don't have to be the fastest. If you have some luck and brains on your side, it can also help."Cronje, who quit his job at the end of last year to start his own investment brokerage, is the oldest member of a large and talented South African team that broke a combined 12 national records in Olympic events so far this season.The top medal hopes are Wayde van Niekerk in the men's 400m and Sunette Viljoen, who will aim to live up to her No1 world ranking in the women's javelin.There are others who could make the podium too, like Caster Semenya, who is showing a late return to form as she bids for a third world championship medal, which would make her South Africa's most successful competitor in this showpiece.Semenya is one of four South Africans to have won two medals, the others being late 800m star Mbulaeni Mulaudzi, high jumper Hestrie Cloete and 400m hurdler LJ van Zyl, who is also in the squad.But Cronje cautions against making medal predictions in the Chinese capital."As long as we can get more and more people into the finals, those finalists will turn into medallists at some stage of their life," he said, pointing to himself - a world championship medallist at 31.Cronje took some hard knocks to achieve his success, such as his elimination from the first round of the 1500m at the 2009 world championships in Berlin, Germany, where "I was in the best shape of my life"."I already saw myself in the final. I looked at the lineup, thought there's maybe one or two who are decent competitors, that should make it easy.mini_story_image_hright1But at the bell the runners behind him attacked and he got blocked in and dragged to the back of the field."I didn't have all that much experience . I totally went into a panic. When you panic and start stressing, all your muscles start [bunching]."Your body doesn't work [properly]. I remember the next day I was so stiff, so sore. It wasn't even a hard race but I was so sore - my neck and shoulders, arms and back. Just from that lap of stress."Cronje also got boxed in at the 2013 showpiece in the Russian capital, but then he kept calm."I just wanted to finish top five. Even through the back straight that was on my mind. Even with 100m to go ."Only in the last 80m did I realise that I can actually win a medal. If I went [in] to win the race [from the start] I would have gone too hard too early."He admits there were times he didn't take athletics as seriously as he might have, like the last occasion he went to Beijing, for the 2001 World University Games, when he was a first-year student.And the last time he went to the Olympics - in Athens, Greece, in 2004."I thought 'okay, this is my first Olympics, I have a lot to come so I'll just be a tourist', and the next two Olympics [2008 in Beijing and 2012 in London] I was injured."Now I look back and think maybe if I had tried a bit harder I could have been in a final [in 2004]," he said, adding that young athletes should use every opportunity they get.That's what Cronje intends to do between now and the Rio Olympics next year...