Cape Town - Springbok No 8 Duane Vermeulen says they can still improve as tougher challenges lie ahead in the Rugby Championship.The Boks produced arguably one of their best ever showings on Saturday when they crushed Argentina 73-13 at FNB Stadium.Vermeulen returned to action for the first time since injuring his knee in a Super Rugby game in May, and was impressive as South Africa "outmuscled" their South American opponents."I really enjoyed it," Vermeulen told the Beeld website. "It was probably a bit tough for them up here (Johannesburg) and I think the height above sea level caught them out a bit. Maybe also the fact that they had to travel. "But next week (Saturday) is different. A different crowd, a different field," he said, referring to the away game against the Pumas in Mendoza.The burly No 8 also said there is room for improvement."We can still improve a lot, even though we set a standard (on Saturday). Big and strong opponents await us, and to play away from home will be tougher."Saturday's Test in Mendoza kicks off at 21:10.