Liam Plunkett's six off the last ball to tie the first one-day international with Sri Lanka masked a "rusty" England display, says captain Eoin Morgan.
Chasing 287, England slumped to 82-6 before 93 from Jos Buttler, Chris Woakes' 95 not out and Plunkett's final blow levelled the scores.
"I'm very proud of the individuals today, but they mask our overall performance," said Morgan
"We were rusty, particularly with the bat."
On a blameless Trent Bridge pitch, England lost four wickets in the first 50 balls, then, after Morgan made 43, the captain and Moeen Ali departed in the space of two overs.
"We just got out," the 29-year-old told BBC Sport. "As a batsman, that's not good early on in your innings.
"It was almost so bad that we can't look too hard at it. We have to draw a line under it, go back to basics, focus on the things we do well and take that to Edgbaston for the second game on Friday."
They were rescued by a seventh-wicket stand of 138 by Buttler and Woakes, the latter registering the highest ODI score by a number eight.
After Buttler holed out to long-off in the 43rd over with 67 still required, England struggled to find the boundary and were left with 30 to get from the final two overs and 14 off the final six balls.
Pace bowler Nuwan Pradeep repeatedly made scoring difficult with accurate yorkers but, with Plunkett on strike to the final delivery, a length delivery was lofted over long-off for only England's eighth tie in 665 ODIs.
"I've been striking the ball quite nicely for Yorkshire and I felt in decent nick," said Plunkett.
"I'm just thinking 'I'm going to back myself to hit it straight'. I managed to get a bit of wood on it and it was nice to see it sail over the rope."
For Woakes, his effort with the bat comes after a successful return to the Test side, averaging 52.50 with the bat and taking eight wickets in England's 2-0 series win.
"I suppose it feels like a win, from the position we were in," he said. "To be fair to Pradeep, he didn't really miss many yorkers but unfortunately for him he missed that last one and 'Plunksey' cleared it out of the ground."
For Sri Lanka, the late drama denied them a first victory over England on the tour, with four ODIs and one Twenty20 remaining.
"I thought we were pretty poor in the field," said captain Angelo Mathews. "If we had fielded well we could have won it easily, but we didn't.
"It was a good game. It was swinging both ways. A couple of mistakes here and there, falling off the length and lines and we paid the penalty."