Joe Root defends Jamie Smith after keeper rinsed over 'one of the dumbest shots you'll ever see'

Joe Root has defended Jamie Smith after former Australian coach Justin Langer described the keeper's dismissal as "one of the dumbest shots you'll ever see".

Smith looked largely uncomfortable - to put it nicely - at the crease as he supported Root throughout the first session of day two at the SCG on Monday.

He should have been out in consecutive deliveries to Cameron Green, only for the first one to be called a front-foot no ball after he was caught out at cover, and the second one to sail between the Australian wicketkeeper and first slip after a thick edge.

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Smith miraculously played his way to 46 and was zeroing in on a half century before lunch in the fifth Ashes match.

Australia, desperate to break the 94-run partnership between Root and Smith, decided to throw the ball to part-time bowler Marnus Labuschagne just before lunch.

Labuschagne was sending down rank half-trackers, one of which was called a wide and which shouldn't have genuinely troubled a serious Test batter.

But Smith - who averaged less than 20 throughout this series before Monday's knock - decided to smack Labuschagne's short ball to the off side, where he was caught by Scott Boland.

"Jamie Smith, what have you done?" former English player Isa Guha said on Fox Cricket.

"Too many times in this series Australia has been handed a gift, and there is another."

At the close of play, Root understood the frustration from fans but explained Smith would be even more irate.

"There's no one more frustrated than the guy who's lost his wicket," he said.

"The guy's worked incredibly hard and you're trying to find the best way possible to get to where you want to get to. I understand why people see the game differently and there are times when you have to be able to absorb pressure and understand at different moments when to put it back on.

"But I think that was an opportunity and I back him 100 per cent to take that next time around as well."

Root's comments came amid more criticism of Smith for picking out the only man at extra cover.

Aussie women's captain Alyssa Healy said, "there was one man in front of point on the off side, and he's picked him out".

"I know this is the way they play and the way they want to approach it, but you cannot honestly tell me he's going to walk back into that change room and be patted on the back," Healy added.

Former Aussie fast bowler Brett Lee could only laugh.

"It's a rank bumper outside off-stump, but what was he doing? What was Jamie Smith thinking?" Lee said.

"It was a poor shot … It's a filthy shot."

But the harshest criticism came from Langer.

"Not for the first time this series, Jamie Smith has played one of the dumbest shots you'll ever see in Test cricket," Langer said on Seven.

Fellow former Aussie batter Simon Katich was equally disgusted but admitted he almost expected it from Smith.

"It's not a surprise though. That's a poor shot. He's gifted his wicket there. It's poor batting," Katich said on SEN.

Smith, 25, averages above 40 from his 20 Test matches and is highly regarded by the hierarchy in England.

But his tour of Australia has done nothing to impress anyone, as he's struggled with the gloves and looked largely village with the bat in hand.