Former England captains Nasser Hussain and Michael Atherton say Steve Smith may not be the same all-conquering batsman he was, when the 30-year-old returns from his concussion scare.
Australia are confident they can retain the Ashes in Leeds without Smith, who has been officially ruled out of the third Test because of concussion.
Smith, recovering from a delayed concussion after being struck on the neck by a Jofra Archer bouncer at Lord's, will not take the field when the series continues in Leeds at Headingley.
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Smith is in far better spirits than on Sunday, when he became the first concussed cricketer to be substituted out of an international match, but the tight turnaround was always going to count against him.
"He was probably a couple of days off being fit," coach Justin Langer said.
"It was really a no-brainer.
"Like all players, he wants to play ... but he understands as well he's not 100 per cent yet."
Smith hopes to return from concussion in next week's low-key tour game against Derbyshire, having run out of time in his bid to be fit for the third Ashes Test.
The former skipper, who was restricted to walking and shadow batting at Tuesday's training session, will be regularly assessed in the coming days as he recovers from the blow.
Team doctor Richard Saw has complete control over when Smith is allowed to start stepping things up.
He is expected to return for the fourth Test at Old Trafford, which starts in a fortnight.
However, Hussain and Atherton have raised concerns that Smith may not come back the same player, such is the nature of the fright that he suffered at Lord’s.
Hussain said if Smith does return for the fourth Test, it will be crucial to see "how he reacts mentally" when facing Archer again.
“Whoever you are and however good you are, you never like facing truly fast bowling and once you have taken a serious blow like that things can change," Hussein wrote for the Daily Mail.
A huge part of Smith's success is his unorthodox approach to batting, his odd mannerisms and quirky, yet brilliant technique that have left the best bowlers in the world searching for answers on how to stop him.
Part of Smith's quirkiness is an almost obsessive compulsive approach to his batting, adopting superstitions like Rafael Nadal is famous for on a tennis court.
Atherton reasons that in the wake of the Archer incident and with Smith likely to adopt the neck guard he admitted to finding uncomfortable, whether the Aussie star will be able to bat with the same effectiveness.
“Will this superstitious and meticulous player adapt his protective equipment, adding the neck protectors that, he says, feel uncomfortable? We will have to wait until Old Trafford to find out,” Atherton wrote for The Times.
Aussies won’t resort to bouncer barrage
Australia coach Justin Langer has told his side to avoid being drawn into a bouncer battle in light of Smith's absence for the third Test.
But rather than face another Archer bouncer barrage in his competitive return, Smith is aiming to be ready for a three-day clash in Derby that starts on Thursday week.
"It'd be great for him, rather than just doing it in the nets or having throwdowns, to play that practice game. It could work out really well,” Langer said.
"We know what he's like, so look out the Derbyshire bowlers.
"I'm sure if he passes what he has to go through he'll be right to play that game."
Langer insisted his side would not be sidetracked from their goal of becoming the first Australia side in 18 years to win an Ashes series in England.
"We know what our plans are to beat England," Langer added.
"It's not an ego game," the former Australia opening batsman insisted.
"We're here to win the Test match, not to see how many bruises we can give. That's not winning Test matches, trust me. You can't get out with a bruise on your arm.
"I'm sure the bouncer will still be part of every bowler's armoury, if it helps us get batsmen out then we'll use it, otherwise we'll keep sticking to the plan."