Both Ishant and Rohit are running out of time to travel to Australia and be part of the Test series.
ESPNCricinfo has also learnt that their hopes of taking part in the last two Tests hinge on swift and decisive action from the BCCI. To be in contention for the third Test, Ishant, who has regained bowling fitness but needs four weeks of workload to be ready for the rigors of Test-match play, will have to board a plane almost immediately.
The 14-day hard quarantine rule in Australia means he can start training only after two weeks; add another four weeks of preparatory training, and he can only be match-ready for the third Test, starting on January 7 in Sydney.
Rohit will only be cleared to travel by the NCA on December 8 at the earliest, and though he does not require the same amount of time to be match-ready, he would still have to serve a 14-day hard quarantine, which will keep him out of training until December 22.
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Rohit suffered a grade two hamstring tear during the last stage of the IPL 2020 and it could take him another two weeks of rehabilitation to get to "70 or 80% readiness", according to a BCCI functionary. The functionary also believes Rohit would have had a better chance of featuring in the Test series had he flown directly to Australia with the other squad members from the UAE.
Ishant has regained fitness and increased his bowling workload, but issues are about his match fitness which can only be ascertained once he's in a position to bowl at least 20 overs in a day.
"If there is a T20 game and he needs to just bowl four overs, Ishant is good to go immediately, but for him to get back to Test-match fitness, he needs four weeks of proper bowling still," a BCCI source said.
Even if Ishant and Rohit were to fly out in a day or two, the hard quarantine would mean each of them needing to isolate himself in his hotel room for 14 days. This will mean neither is able to take part in the two warm-up games that precede the first Test in Adelaide, which begins on December 17.
The 32-member India contingent has begun training in Sydney while in quarantine after flying in directly from UAE after completion of the IPL, where they were in a bio-bubble. However, the same concessions can't be afforded to Rohit and Ishant upon arrival, since they aren't in a biosecure bubble at the NCA where they are currently training.
Shreyas Iyer could benefit from Rohit Sharma missing the Test series, as he is already a part of India’s red-ball plans as cover for Virat Kohli, but is yet to make his Test debut.
On the bowling side, India has the likes of Jasprit Bumrah, Umesh Yadav, Navdeep Saini, Mohammad Shami, and Mohammed Siraj in their Test squad. They also have reserve bowlers to choose from.
(ESPNCricinfo inputs)