Pakistan captain Inzamam-ul Haq blamed his team's batting collapse in the first innings for the 195-run defeat in the second Test against India on Sunday.
The visitors were bowled out for 226 in the final session of play at the Eden Gardens on Sunday to give India a 1-0 lead in the three-match series after the first Test in Mohali was drawn.
"Not taking the first innings lead was the turning point," a disappointed Inzamam said.
"Had we done that, the result might have been different.
"If the batsmen had shown more responsibility we could have drawn the Test. It was difficult scoring 300-350 runs on this pitch."
Pakistan were coasting on 273 for two in reply to India's first innings 407 all out after day two, but lost the last eight wickets for 112 runs and were dismissed for 393 on the third day.
Rahul Dravid then hit his second hundred of the match to boost India to 407 for nine declared in the second innings and help set a huge 422-run fourth innings target.
It was Pakistan's seventh defeat in 10 matches, including a 3-0 rout in Australia in January.
Pakistan's batsmen had fought to salvage a draw in the first Test in Mohali after going into the final day just 53 runs ahead with four wickets in hand.
"Today, if we had not lost a wicket for one full session in the afternoon, we could have saved it," Inzamam added.
He praised Indian leg spinner Anil Kumble, who captured seven for 63 in the second innings to return match figures of 10-161.
"Kumble is a great bowler and he was tough to handle on a fifth day pitch of inconsistent bounce," he added. "We need a combined effort now; hopefully that will come in Bangalore."
Pakistan received a boost for the final Test in Bangalore, starting on Thursday, when fast bowler Rana Naved was declared fit.
He missed the Kolkata match due to a shoulder injury and rookie left-armer Mohammad Khalil went wicketless.