Ed Cowan has described David Warner as a "walking wicket", saying most people would have agreed with Mitchell Johnson's scathing comments about the retiring Test opener.

Former Australia coach Justin Langer also weighed into the Warner debate, saying he hates it when former teammates air their grievances in public.

Johnson lit the fuse earlier this month when he questioned whether Warner deserved a hero's farewell given his role in the sandpaper ball tampering scandal in 2018.

The former pace ace also said Warner's form was so poor he didn't deserve to be selected.

Langer isn't a fan of the public criticism levelled at Warner.

"In simple terms, I hate it when men from the rare club of playing cricket for Australia air any of their grievances publicly," Langer wrote in his column for The West Australian.

"I believe in a simple ethos of, 'praise in public, criticise in private'.

"In other words, if you want to say something publicly be positive and use the opportunity to praise the person you are talking about.

"In contrast, if you want to criticise someone, look them in the eye and tell them how you are feeling."

Warner has averaged 22.8 across nine Tests this year and just 30.1 across 11 Tests last year.

The 37-year-old will retire at the conclusion of the three-Test series against Pakistan, which begins in Perth on Thursday.

Cowan played 18 Tests for Australia between 2011-13, partnering Warner at the top of the order for most of that period.

The 41-year-old agreed with Johnson's points about Warner, but felt it could have been delivered better.

"Mitch Johnson is saying what 90 per cent of people in the pub have been thinking," Cowan told The Grandstand Cricket Podcast.

"What I didn't love ... was the tone. There was a sense of anger or injustice to it.

"But the actual points around selection - statistically David Warner probably shouldn't be in the best XI - I think most people would agree with."

Warner's impending retirement has raised an important question - how will Australia replace him?

Cameron Bancroft, Marcus Harris and Matt Renshaw have all been floated as options if Australia opt for a like-for-like replacement.

But Cowan would prefer to see a reshuffle of the current line-up, with either Travis Head or Marnus Labuschagne opening.

"That allows you to pick your best six batters, probably with a Cameron Green and a Mitch Marsh in the team batting at five and six, and it reshapes the team," Cowan said.

"With Marnus opening the batting - he's walking out at one for none anyway. David Warner has been a walking wicket for two years now.

"So at least he (Labuschagne) knows when he's going to bat (if he becomes opener) and he can prepare."