Centurion, Sep 15 : South Africa fast bowler Anrich Nortje has been ruled out of the remaining two matches of the five-match One-Day International (ODI) series against Australia due to a lower back injury, Cricket South Africa (CSA) said on Friday. "The 29-year-old underwent scans and consulted with a specialist this week, and will start bowling again this weekend under the supervision of the Proteas medical team. A further update will be provided in due course," it said in a statement. However, CSA has not named any replacement yet. The loss of Nortje has been further compounded with news that in-form skipper Temba Bavuma will also miss the penultimate clash of the five-game series with a right adductor strain. Aiden Markram will lead the Proteas men in the fourth ODI in the absence of Bavuma. "ODI captain Temba Bavuma is unavailable for selection for the fourth ODI at SuperSport Park, Centurion on Friday. Bavuma has a right adductor strain and as a precautionary measure, he has been ruled out of the match," CSA said. After suffering 3-0 loss in T20 series, South Africa are trailing Australia 0-2 in the five-match ODI series and will need to win the next match to keep the series alive. /IANS