Johnson in 'good head space' for Ashes - bowling coach
Australia fast bowler Mitchell Johnson celebrates a wicket during the Twenty20 international against England in Southampton, southern England, on August 29, 2013
Johnson has admitted the goading England supporters' group was his Achilles heel during Australia's Ashes humiliation at home three years ago.
Johnson's possible reappearance is expected to set off the chanting Barmy Army supporters if the left-armer earns an Ashes recall for the November 21 opening Test in Brisbane.
But McDermott said the in-form Johnson is in a mental and technical position where he will be resolute enough to shrug off his past nightmares and play a leading role for Michael Clarke's Australia team.
"He's in a good head space at the moment. I think it would take a lot for that to be taken away from him," McDermott told reporters.
"He's confident about what he's doing with the ball and the pace that he's bowling, so who cares about the Barmy Army.
"They're off the field. They don't stop him from getting lbws, caught behinds and clean bowleds, so who really cares about them."
Johnson has played one-day international cricket exclusively since the fourth Test in Delhi in March, and he is now preparing for the Ashes.
The 31-year-old is set to play for Western Australia in their four-day Sheffield Shield match against South Australia in Perth next week.
McDermott will fly to Perth to be with 51-Test Johnson throughout the Shield game from next Wednesday before he assembles a first Test fast bowling group in Brisbane on November 14.
Injuries to James Pattinson and Mitchell Starc have opened up a position in the attack, and former Test paceman McDermott said Johnson has stepped up when required.
"Certainly the radar guns are saying that over there and the guys are saying he's bowling really quick," he said.
"He has been moving the ball back into the right handers a little bit so to me his arm path and his seam position seems to be better so we've just got to make sure we keep it that way.
"It's a little bit different bowling with the red ball (first-class cricket) so for him to play a Shield game in Perth will be important.
"I just want him to be relaxed. He looks in a tremendous head space at the moment, he looks confident in what he's doing."
Johnson, who made his Test debut in 2007, has taken 205 wickets in his 51 Tests at 30.93
McDermott is also pleased with front-line quicks Ryan Harris and Peter Siddle and says the likes of James Faulkner, Ben Hilfenhaus, Josh Hazlewood, Nathan Coulter-Nile and Doug Bollinger are also applying pressure.