Cape Town - Proteas bowling coach Allan Donald is busy studying video material of Sri Lanka's players ahead of their tour to South Africa. Donald is currently at home preparing on his own for the upcoming Test series which starts with a Test match on December 15 at SuperSport Park in Centurion."I'm currently busy with my own planning. I'm looking at their key players - the core of their batting line-up - but there some players here and there whom I'm not very familiar with," the former SA opening bowler told the Volksblad newspaper.Donald singled out Kumar Sangakkara, Mahela Jayawardene and Angelo Mathews as the danger men for South Africa's bowlers.Donald said they would have to "think carefully" on how they are going to silence Sangakkara - currently the No 1 ranked batsman on the ICC rankings.He is also wary of Mathews. "He can take a game out of your reach. He is one of the batsmen against whom we'll have to bowl aggressively. We can't afford any loose deliveries against him as he is someone that can get the scoreboard rolling quickly," said Donald.Another former SA opening bowler, Shaun Pollock, believes the Proteas have the bowlers to trouble the Sri Lankans. "Morne Morkel bowls well to left handers in any case," said Pollock.