Mickey Arthur admits Pakistan's fielding is a "real worry" going into the World Cup.

Arthur, the Pakistan coach, believes the standard of fielding was the key difference between the sides in the ODI series between England and Pakistan.

But he insists his side are "working damn hard" to improve and felt that Pakistan's batting - they reached 340 three times during the series - gave them "a fair amount of positives" to take despite the 4-0 scoreline. In particular, he felt the introduction of a couple of new players - who hadn't been part of the regime that had worked hard on improving Pakistan's fielding over the last couple of years - might have resulted in the standards dipping.

"Our fielding has been very disappointing," Arthur said. "That's been the massive difference between the two sides. If you look at the games in Southampton and Nottingham, going into the last five overs, it was anybody's game. We competed really well.

"The one difference has been our fielding and that's a real worry for me because we are putting a hell of a lot of effort into it. And there's not a massive amount of reward for us there at the moment. We'll just keep knocking away at it to make sure we get it up to speed.

"We have a couple of new, young players who weren't part of the regime previously. We are trying to bring them up to speed as quickly as we can. It's something that hasn't gone unnoticed with us and it's something we are disappointed about. We need to do a bit of work on that, for sure.

"Fielding is about attitude and wanting to get out there and get it done. Our boys' attitude has been outstanding through this series. They know they've been short in this department and they are not happy about it. They are working damn hard at it."

Despite his disappointment in his side's fielding - and, to some extent - and bowling performances, Arthur remained "very confident with the players we've got."

"We sit here having taken a huge amount of positives out of this series," he said. "I thought our batting has gone to another level. I thought we batted extremely well.

"Our bowling has been average at best and our fielding has been average at best but we've batted really well. People, coming to England, said we were a 280 team. We've dispelled that and that's given our batting unit a massive amount of confidence. I'm taking a fair amount of positives in that department.

"The other thing is we've played against a team who are No.1 in the world in their own conditions. There's not too many teams who will arrive in England as prepared as we are in terms of the competition we've played against and match fitness.

"We've got a couple of days now to regroup, two warm-up games and then we'll go. I'm very, very confident with the players we've got. We need to sharpen up on a couple of disciplines but we'll certainly get there. We'll be good."

While Arthur declined to confirm the make-up of Pakistan's final 15-man squad, he did say that Mohammad Amir was sufficiently recovered from chickenpox to be considered available for selection.

"Mohammad Amir trained yesterday for the first time," Arthur said. "It's the first time he was allowed to train. He had 25 minutes on a bike and then a gym session. He had another one today so, if he's selected, he will be ready to go."