"We committed the cardinal sin of losing two in players in one over and the allowed India to build pressure."
The 23-year-old Chahal became only the second bowler in T20 cricket to get six wickets in an innings.
Root's LBW during the last over paved way for India's return in series.
Before the match, Kohli had led India in 19 international games at home without a defeat.
India looks to keep the two fresh for the Test series against Australia.
Wahab Riaz, Faheem Ashraf included in 20-man shortlist for England Tests
'We maintained a reasonable run rate considering the conditions' - Shan Masood
The flair, the calmness and the promises: Pakistan's rhetoric in the lead up to first Test
'Plans underway to stage remaining PSL matches this year' - PCB
Babar Azam fluency tames sloppy England on rain-curtailed opening day
Sohail Khan bags five wickets as Pakistan's leading batsmen flounder
Broad takes 500 Test wickets, Woakes bags five as England reclaim Wisden Trophy
Pakistan grapple with selection predicament as fired up England eye strong start
Team Green put on improved batting display after Naseem Shah shines again
Haris Rauf set to join Pakistan squad in England after returning two negative tests