The tourists were bowled out for 67 runs, a total which the home side passed in 12.1 overs to take a 2-1 lead in their one-day international series.
The Sri Lanka captain told Sky Sports News: "The conditions were for both teams. We had to dig deep when it comes to batting because we played some poor shots as well as the English bowlers bowled pretty well.
"All in all it was a poor performance. The poor shot selection was the main reason why we got the 67. The wicket was doing a little bit. It was better after the first ten overs but it was a poor performance.
"The English team is very hard to beat on home soil. But I think I've got the team to do it. We've showed in the past."
The teams play again at Lord's at the weekend.