Leeds - The Proteas suffered injuries to key players during the current Test match against England at Headingley.Scorecard after Day 4Alviro Petersen, Graeme Smith and Jacques Kallis are the affected players. “Alviro Petersen’s hamstring strain is coming along, he is still about seven days away from full fitness and if he has to bat in this Test match he will,” said team doctor and manager Mohammed Moosajee. “Graeme Smith is managing with a heavily strapped left knee. He jammed his knee into the ground while fielding a ball at the boundary yesterday (Saturday) evening. We assume that he may have damaged something from a posterior aspect, either his cartilage or meniscus but we will have a proper look once the Test match is over. However, Moosajee said Kallis’s fitness is their biggest worry. “He (Kallis) has an issue with lower back spasms, he has had this problem before and with his long career and with him being an all-rounder, the load that he has to handle has affected his back. He strained it while diving for a catch in the slips yesterday and he will be closely monitored overnight to see how he responds to treatment. If he has to bat we will make sure that he is well supported.”South Africa ended Day 4 on 39 without loss in their second innings, a lead of 23 after England were dismissed for 425.Jacques Rudolph, opening in place of Petersen, was unbeaten on 21 while Smith was on 17 as he continued to bat despite being injured.South Africa scored 419 in their first innings.