Marian Vajda - Marian Vajda, a Slovakian, started coaching Novak Djokovic in 2006, and over the next few years started to make an impression on his game, his physical fitness, and his diet. Having struggled with lack of stamina, and lack of mental toughness too, Djokovic was in need of an overhaul if he was to break the supremacy of Federer and Nadal. Marian worked hard on Djokovic’s serve. “When you have a good serve, you shorten games and hold easily,” Marian Vajda said in an interview with BBC Sport. What still needs work? “His approach to and position at the net” says Vajda.