Cook will be after an improvement from his bowlers after they went down by 25 runs in game one of the seven-match series.
Sri Lanka scored 94 runs from their final 10 overs to post an imposing total of 317-6 in Colombo and it proved beyond the reach of the tourists, who mustered 292 in response.
Moeen Ali was the star of England's response, hitting 119 from 87 deliveries, but he did not receive enough support - only three other batsmen scoring 20 or more.
Despite the defeat, Cook remained upbeat and sang the praises of the opener.
"Moeen played a fantastic innings to get us going," Cook is quoted as saying on the England and Wales Cricket Board website.
"We've got a lot of talent. He showed us the way.
"The first 10 overs, I don't think we bowled as well as we should have done. We dragged it back pretty nicely in the middle overs.
"It was a really good game of cricket…[it is] frustrating to come out of at the end because we scored a lot of runs.
"It shows that we're doing a lot of good things in patches - just not able to put it all together."
Alex Hales appeared set to partner Cook at the top of the England order during the one-day series, but Moeen jumped ahead of him with a brisk 56 in a tour match against Sri Lanka A.
And England's decision to go with Moeen was justified as he hit the third fastest one-day international century for the nation.
Moeen smashed 11 fours and five sixes in his knock and a repeat would go a long way to helping England level the series.
Harry Gurney risked losing his spot with 0-66 off 10 overs, though.
Tillakaratne Dilshan, Kusal Perera and Mahela Jayawardene all scored fifties for Sri Lanka in the series opener - while the late hitting of Jeevan Mendis (30) and Lahiru Thirimanne (27) proved crucial.
Spinners Rangana Herath and Ajantha Mendis took two wickets each and caused England problems.
Inclement weather threatened to postpone the first match of the series and given the wet season in Sri Lanka, a repeat would not surprise.
Reserve days have been scheduled for five of the seven contests, though, and one is in place for Saturday's clash if needed.