MITCH PHILLIPS, ROZANNA LATIFF and SIMON EVANS TOP-RANKED Novak Djokovic had his dreams of tennis gold dashed on Friday while Ethiopia's Selemon Barega felled the reigning world 10,000 metres Olympic champion, on a day of upsets that saw doping allegations surface at the swimming pool. Serbia's Djokovic was aiming to become the first man to complete the Golden Slam - Olympic gold and all four majors in the same year - but was undone by fifth-ranked German Alexander Zverev who fought back after losing the first set. The two men embraced briefly at the net and Zverev appeared to sob…