Captain Eoin Morgan said that England are “not the finished article” in one-day cricket after their six-run defeat by Scotland in Edinburgh.
England are the number one ranked side in the world but were beaten after conceding 371-5 against the Scots.
“Scotland played extremely well. They brought their best game and we didn’t,” Morgan told BBC Sport.
“We will make mistakes. Today we made mistakes and hopefully we can learn from them.”
England have shown constant improvement in 50-over cricket since going out of the 2015 World Cup in the first round.
Before their trip to Scotland, they had lost only once in 10 series and they are the favourites to lift the World Cup on home soil in 2019.
However, in glorious batting conditions, they were hit by a brilliant 140 not out from Calum MacLeod that propelled Scotland to the fourth-highest total made against England in ODIs.
“Our bowling strayed a little bit and, on a belting wicket, we got punished,” said Morgan.
Jonny Bairstow’s 54-ball century looked to have England in charge of the chase but they slipped from 220-2 to 276-7 and were eventually bowled out for 365 with seven balls remaining.
Morgan added: “Bairstow was exceptional and we looked like chasing it but a few errors hurt us.”
England now move on to a five-match ODI series against Australia, which begins at The Oval on Wednesday.
Morgan believes that, despite the defeat, the match against Scotland leaves his side better prepared to take on their fiercest rivals.
“Today was a really good run out,” he said. “Usually, leading into a series we have a few days of training, then straight into it.
“Hopefully we will learn going into Wednesday’s game.”