During Australia's tour of the West Indies in early 2012, Siddle suffered another back injury and had to fly home early. Siddle had signed for English county Essex for the 2012 Friends Life t20, England's premier Twenty20 competition, but due to his injury he was unable to fulfill his contract with the club. Siddle returned to the Australian Test team for their series against South Africa at the end of 2012. Whilst out injured, he decided to become a vegetarian. The series was very difficult for Siddle because of the very heavy workload he faced. In the first Test of the series at the Gabba, he was forced to bowl 53 overs in a draw and in the second Test at the Adelaide Oval he bowled 63.5 overs — the most by any Australian fast bowler in a single Test match in the 21st century, as his workload had been compounded by an injury to teammate James Pattinson mid-match. Australia needed to bowl South Africa out in the final two days of the Test match to avoid a second consecutive draw and Siddle was the most successful Australian bowler with four wickets. Whilst showing clear signs of exhaustion throughout the final day, Siddle pushed through and took wickets late in the match but was unable to get Australia the win.