After leading England on a failed attempt to regain the Ashes, Joe Root has a familiar headache in the fifth and final Test: How do you stop Australia's star batsman Steve Smith scoring buckets of runs?
Smith has scored 144, 142, 92, 211 and 82 in his five innings in the series so far. He missed one innings in the second Test and the entire third Test - which England won by one wicket - because of a concussion.
The 30-year-old has been the single biggest difference between the two teams throughout the series.
Returning to Test action following a 12-month ban for his role in a ball-tampering scandal, Smith has - so far - scored 671 runs in this Ashes series at an average of 134.20. It has lifted his career Test average to 64.81 and has been the kind of performance that has drawn comparisons with Don Bradman, who is widely regarded as cricket's greatest batsman.
Smith was the No 1-ranked batsman in Test cricket before he was suspended last year by Cricket Australia. He regained the top ranking from India captain Virat Kohli last week.
Tim Paine, who replaced Smith as Australia's Test captain last year, described his predecessor as the "best player I have ever seen".
"He is just a genius and I never had any doubt he would come back and be the player he was," Paine said. "The scary thing is he's getting better."