Who would have predicted that a tennis player who started the year with a ranking in the nine hundreds would be holding the winner’s trophy at the US Open? Even at the start of the tournament when Sloane Stephens held a ranking of 85, few would have tipped the unseeded player for the title.Predicating outcomes of city marathons is one of sport’s high risk occupations, even when proven Kenyans line up at the start. And expect Sunday’s Sanlam Cape Town Marathon to again deliver surprises before the podium dust has settled.The reason for the marathon’s unpredictability is not hard to fathom. The many variables in road racing - including training, nutrition, motivation, equipment, physical and mental wellbeing, externalities including weather, past results against the same competitors, race tactics and many others are multiplied by the 42km on the road. Blistering due to poor shoe selection, for example, might be inconsequential in a 10km race, but will be of paramount importance in a marathon. Stomach complaints due to sub-optimal pre-race diet could be ignored for twenty or thirty minutes, but never over the two hours and more which are needed to complete a standard marathon.Over the past three years, there have been three major surprises in the outcomes of the senior title races at Cape Town, namely Shadrack Kemboi’s victory in 2015, Lungile Gongqa’s superb second place in the same year and Tish Jones’ amazing victory over Ethiopian and Kenyan rivals last year.The 29-year-old Kenyan, Kemboi, had been based in Johannesburg for some time leading up to the 2015 race and not been a part of the invited elite squad of athletes from East Africa, Japan and Europe, but had the motivation to prove his worth and won in 2:11:41 - five minutes faster than his previous best.Another shock that year was the stellar performance of South African marathoners, with Gongqa, Michael Mazibuko (3rd) and Sibusiso Nzima (6th) shutting out the more favoured invited foreign athletes, who were surprisingly off the pace in the second half of the race.At last year’s marathon Cape Town celebrated when their “adopted daughter”, British athlete, Tish Jones, powered through to victory in the women’s competition, winning in a huge personal best time, but who would have predicted the demise of the favoured Ethiopians who were unable to match Jones’ strong finish on the day?One of the biggest, and heart-warming, marathon surprises in recent years was Josia Thugwane’s 1996 Olympic Marathon gold medal. The diminutive Mpumalanga athlete still bore the scar on his chin from a bullet from an attempted hi-jacking a few months earlier when he crossed the finish line to win by five seconds. In addition, he had required medical treatment for a back injury sustained while jumping from the moving car to escape. Will the seeded runners prevail on Sunday. Or will the honours go to the “unknown soldier”, like Sloane Stephens looking for an opportunity to break into the big time?