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 allrounder Ben Stokes through injury would be a big blow for the side.
"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.
