Michael Clarke hails Mitchell Johnson "X-factor" for Australia

Michael Clarke has no doubts that Mitchell Johnson is providing Australia with an "X-factor" against England in the Ashes series.

The bowler has tormented the tourists throughout the opening two encounters of the series to take 17 wickets, with the hosts extending their lead to 2-0 thanks to a comfortable 218-run victory at the Adelaide Oval on Monday.

"He has always been an X-factor, with bat and ball. He's as good an athlete in the field as you'll see," Clarke told the press.

"Mitch has always had that. It's just about working out how to use him best in your team."

Australia can win back The Ashes and end a run of three straight series losses to England with another victory in the third Test, which gets underway at The WACA in Perth on Friday.