Argentina coach Hernan Rouco Oliva believes smaller countries will continue to test the established powers after watching Tunisia make an indelible mark against South Africa and then give his own team a fright. Oliva was struck by Tunisia's clinical performance against the South Africans and the unheralded team continued to surprise him after they took a shock 5-0 lead against the Pumas before succumbing 24-5. 'The smaller nations are improving all the time because the game of sevens is suitable for teams who can find speedy players,' said Oliva. 'All you really need are speed and defence concepts like tackling, organisation and discipline. You can build a good sevens team quicker than 15s.' 'Tunisia are improving a lot. They have a good training system. We couldn't play our normal attacking game in the open side. We made a couple of errors in the passing and handling so the match was very tight [in the first half]. Fortunately, we scored a couple of tries in the second half.' Asked whether more small nations could make an impact in the abbreviated game, Oliva said: 'It can happen by the time the next World Cup finals are held. It depends what kind of work these nations want to put in. If they train a lot and study the game a lot, it is possible. 'Any team who play sevens know when you start to lose confidence and you make a couple of mistakes, the other team can beat you. That's what happened to South Africa, who, obviously, are a much better team than Tunisia on paper. But in one match, you can still lose,' said Oliva. 'To beat South Africa is a major accomplishment.''