Nabi, who reported for the IMG-Reliance camp in Mumbai on August 2 for a pre-season camp for the IPL-style football tournament early next year, was the surprise omission from the squad.
Asked about Nabi's omission, AIFF General Secretary Kushal Das said he was not in a position to give reason.
"The national coach would tell the reason," he told PTI.
AIFF Director of National Teams, Subhankar Mukherjee said Nabi was not fit.
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Paul's omission was not altogether unexpected as he had not been in the best of form in the past one year and he was replaced under the bar by veteran Sandip Nandy in India's last international friendly on February 6.
Other notable players left out include winger Anthony Pereira and young Alwyn George who played in the Palestine friendly.
National coach Wim Koevermans also brought back Robin Singh as the third striker in the squad along with captain Sunil Chhetri and uncapped Sporting Clube de Goa forward Dawson Fernandes.
The Indian squad leaves for Tajikistan from here on August 9. They will return here on August 16 and straightaway will proceed to Bangalore for a Preparatory Camp for the SAFF Championships which will be held in Kathmandu from August 1 to 11.
Another set of players will join the squad for the Preparatory Camp in Bangalore which would be announced later.