Ashley Giles has promised to be "ruthless" in his role as coach of England's limited-overs sides. Giles could reflect with some satisfaction on England's ODI series victory in New Zealand - their first such success in the country in more than two decades - but knows he has some tricky decisions to make ahead of the Champions Trophy in June.

Giles' main issue is how to accommodate the return of Kevin Pietersen - rested for the ODI series in New Zealand - into the Champions Trophy side. England's decision to rest players from ODI series - Pietersen in New Zealand and Jonathan Trott in India - allowed Joe Root an opportunity which he grasped impressively, leaving England wrestling with the issue of fitting six batsmen into five available spaces for the June event. While Alastair Cook is certain to play alongside a wicketkeeper and five bowlers, the remaining five batsmen - Pietersen, Trott, Root, Ian Bell and Eoin Morgan - would appear to be competing for four places.

But if anyone feared sentiment may play a part in the decision making - two of those five, Bell and Trott, are former team-mates from his days with Warwickshire - Giles was quick to dispel such doubts.

"I have to be more ruthless as a coach," Giles said. "You are not being nasty, but you've got to make strong decisions. When you drop someone, you always look them in the eye. Sometimes it will fall to the captain, sometimes I might do it, but all you can do is to be honest. If your performance isn't good enough, I'm going to tell you. I don't expect you to like it, but it doesn't change the conviction behind the decision. Players are selected to perform and ultimately we have to pick the side that we think will win games.

"The most difficult decisions are when you leave players out and you never do that lightly. If you don't step in, and everyone else can see you should be doing it, you lose respect quite quickly.

"With the Champions Trophy being in English conditions we have the opportunity to do really well. I'll go away and look very closely at Australia, New Zealand and Sri Lanka, the other teams in our group. But we don't want to get too cute with the game. The formula with which we play is pretty simple but homework on the opposition, like bowling very straight to Ross Taylor, is important."

Giles also plans to speak to the coaches at many of the counties to ensure that their plans and those of England are in harmony. Most pertinently, he will speak to Somerset about their wicketkeeping plans. At present Jos Buttler, now first-choice with the gloves in ODI and T20 cricket, is denied the gloves at Taunton by Craig Kieswetter. Giles hopes to persuade the club to reverse that policy with a view to providing Buttler with more experience.

Somerset are likely to oblige. Not only do they have a record of accommodating England - they drafted Andrew Strauss into their team in 2011 when he required match practice ahead of the India series - they also have a strong relationship with Giles Clarke, the ECB chairman, who was previously chairman of the club. The fact that they are keen to host ODI cricket may not be irrelevant, either.

"I will be speaking to Somerset about both players," Giles said. "Obviously we have a responsibility to Craig, who I'm sure wants to get back playing for England but Jos is keeping for us now.

"Craig wasn't left out of the squad, it was by mutual consent really. The opportunity had gone for him. With Jos taking the gloves and Jonny Bairstow being next in line it made sense on both sides for Craig to go home and get his game in order.

"I hope to speak to most of the directors of cricket at counties about the players involved this winter and how we think they can improve. I can't tell Somerset what to do, but it's pretty obvious that Jos needs to keep wicket now. It is a very different situation for Somerset, though, because they have a duty to help Craig get back into international cricket. I don't envy their position and Jos, Somerset and Craig will have to discuss it."

Somerset would be understandably reluctant to lose either Buttler or Kieswetter. Both were schooled locally and have long careers ahead of them in the game. But, in the long-term, it could be that one of them feel the need to leave for more opportunity elsewhere.

Nor is the issue just at Somerset. Ben Foakes, the England Lions keeper, also requires first team cricket if he is to progress, but is currently denied the gloves at Essex by the continuing excellence of James Foster. Giles may also reflect on the situation at Warwickshire, where Trott tends to open the batting in domestic limited-overs cricket and Bell comes in at No.3; a reversal of their England roles.

While Giles will now return to the UK, his work as England's limited-overs coach continues. Firstly he will stop off in Australia where England Lions are struggling against their Australian counterparts while, following a full series debrief with Cook, Giles will further the planning ahead of the Champions Trophy allowing Andy Flower to concentrate on England's Test plans.

"Cooky is an exceptional bloke," Giles said. "I hope we don't agree on everything because it would be dull but we're singing from a similar hymn sheet on most stuff.

"We had three hours when we talked about a number of things going forward. By the time he gets home a lot of time will have passed so it was important we knocked around ideas and I'll take them home to work on. It was a really good chat.

"Sometimes you do fall into one-day games on the back of a major Test series. It suddenly catches up with you and it's a case of 'let's get the white balls out and get on with it.' But now it's my job to make sure we have a very clean switch between forms. The idea is that I will be looking at opponents and venues for the Champions Trophy very closely now."