Warner's place in the side remains a matter of speculation after his twin failure in Leeds where he fell to Stuart Broad in both innings as England prevailed by three wickets to stay alive in the five-match series.
Warner has managed one half-century in six innings in the series but forged three fifty-plus opening partnerships with Usman Khawaja.
"Davey's obviously a bit of a lightning rod for opinion," Harris told reporters on Sunday.
"But I think they've done really well – as an opening partnership when you can get the team off to a good start.
"Even if you’re not getting the big runs that you want to get, if you can still contribute to the team in some way, shape or form, I think you're doing a job."
Australia are considering ways to accommodate both Mitchell Marsh, who smashed a hundred and grabbed two wickets in Leeds, and the all-rounder he replaced, Cameron Green, who sat out the third Test with a hamstring strain.
Given a chance, Harris said he would grab it with both hands.
"The training we can do now with how big the squad is as a collective... is as good, if not better, than playing a game of cricket," said Harris, who played the last of his 14 Tests against England in Sydney last year.
"All you can do is prepare the best you can. Like we saw with Mitch (Marsh) last game, you never know when your chance will come up.
"If I am called upon, I am ready to go."
