Michael Vaughan paid tribute to Ireland's record-breakers after their stunning victory against England, but he admits his former side has a lot of questions to answer.
Ireland caused an incredible shock by chasing down England's score of 328 with five balls to spare, with Kevin O'Brien smashing the fastest century in World Cup history on his way to a knock of 113.
"I was so impressed with Ireland," said former England captain Vaughan. "They always got the boundary at the right time and they had the batsmen to back up O'Brien, who played the power knock. He was hitting shots out of the ground and it takes a real technique to do that. He was so still at the crease; he hit the majority of balls from the middle of the bat.
"It was a really professional performance from Ireland with the bat. When they were 111/5 I think we all sat here expecting 200 all out for Ireland. Then O'Brien strolled to the crease and smashed England out of the ground.
"Maybe they just became a little complacent, but England have got a lot of questions to answer."
Despite their shock loss, Vaughan believes England can still advance from Group B, provided they improve their fielding.
"I can't put my finger on why the fielding is so bad," he said. "It was poor against the Netherlands, slightly better against India, but against Ireland there were dropped catches, fumbles; it's something that we haven't witnessed from this England side before. I know it's something they work hard on; the approach to fielding in practice is so specific.
"I don't know why they're putting in these performances. Maybe it's the pressure of the World Cup. I'm not having it that they're tired because this team is as fit as any I've ever play in an England shirt. They're just having the odd bad day. They cannot afford to have many more.
"They've now got a big game against South Africa on Sunday. Bangladesh isn't going to be easy in Chittagong. The West Indies are dangerous. They cannot afford any more performances like that in the field.
"There's one absolutely certainty: England aren't out of this World cup yet but they've absolutely no chance if they don't bowl and field better that they did against Ireland."