England have recalled Jonny Bairstow into the ODI side following his superb form, which saw him named man of the series in the 2-0 test series victory against the Sri Lanka.
"It's an unbelievable start. Cookie [test captain Alastair Cook] hands the baton over to me and hopefully I don't let him down," Morgan told reporters on Monday.
"Confidence is a big thing, and it's crucial to build on that confidence we've had going forward."
Morgan added that the absence of hard-hitting all-rounder Ben Stokes through injury would be a big blow for the side.
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"It does affect us because Ben bats at five, doing both roles very well," he added.
"We don't have an answer to back up at the moment, but it does create an opportunity for someone else."
Sri Lanka will have to cope without paceman Shaminda Eranga, who was banned for an illegal action by the International Cricket Council on Sunday just hours after he had been taken to hospital to undergo tests on his heart.
Morgan said that though conditions have posed a challenge to Sri Lanka, he expects a tough fight in the shorter format of the game.
"They (Sri Lanka) have found it tough work since they came here, but ODI cricket comes more naturally to them," he said.
"They are ranked above us, so we won't take them for granted and we are looking to ourselves to build and put performances in."
England play Sri Lanka in five ODI's and a one-off Twenty20 game in Southampton on July 5.
(Reporting by Nivedita Shankar in Bengaluru)
