The home side, batting first with the series evenly poised at 2-2, were in a promising position on 199-6 when Buttler strode out of his crease at the non-striker’s end early and was stumped out by bowler Sachithra Senanayake – halting his run up to pounce.
After consultation from the umpire Sri Lanka captain Matthews asked for the decision to be upheld, insisting his bowler had done nothing wrong within the laws of the game.
England slumped to 219 all out, before Sri Lanka reached their target with 10 balls to spare, much to the annoyance of Cook, who felt Matthews had acted unsportingly.
“I hope I wouldn’t do the same in his position,” said Cook.
“In the spur of the moment it might get the better of you. You have to ask Angelo Matthews why he did it, but I was disappointed with it.”
Matthews explained that Buttler had not only already received a warning from Senanayake for backing up too far in this match, but did so also when trying to steal an advantage in Saturday’s defeat at Lord’s.
And the Sri Lanka skipper said he would back his bowler again should the practice known as “Mankading” occur during the Test series.
“I stick by what we did as it is within the rules of the game,” said Matthews.
“He was taking unfair starts in the last game as well. We gave him two warnings in the spirit of cricket, so we had to go for it.”
England began well, with Cook’s 56 his highest score in 12 one-day international outings. He was supported by Ian Bell (37) with the opening pair putting on 76 until Ajantha Mendis (2-50) made the breakthrough.
Each of England’s top eight batsmen reached double figures, without anyone progressing to trouble Cook as the top scorer in the innings. And, following Buttler’s dismissal, England finished with a whimper, being bowled out with 11 balls to spare as Lasith Malinga (3-50) gobbled up the tail.
James Tredwell spun England back into the ascendency with two quick wickets, but half centuries from Mahela Jayawardene (53) and Lahiru Thirimanne (60), plus Matthews’ 42 off 34 balls saw the tourists home.
England are set to name their squad for the two Tests with Sri Lanka today and Cook has tipped all-rounder Chris Jordan for inclusion.
“CJ has done everything asked of him and given a massive nudge to the selectors,” said Cook.
“His performances, as well as Harry Gurney’s, are the good thing to have come out of this series.”