Rashid Khan out of T20 series against India because of back injury.
Rashid Khan's November injury needed surgery, extending his recovery beyond expectations.
Khan, unfit for play, joins team for ongoing rehab during matches
Captain Zadran admits Khan's absence, crucial for experience, poses a significant challenge for team.
At 25, Rashid Khan hailed as a top Afghan T20 player, IPL regular since 2017.
Zadran stresses team's need to adapt, prepare for challenges without Khan
Afghanistan is scheduled to play three T20 matches against India from January 11 to 17.
Post-injury, Khan withdrew from T20 franchise leagues in Australia and South Africa.