When Boyd Rankin's second ball of his England one-day debut - against an Ireland side who he had represented 37 times at the same level - disappeared so far down the leg side that Jos Buttler couldn't gather it there was a fear the occasion may get the better of him. That he ended with a career-best 4 for 46 provided Rankin with a major tick in Ashley Giles' coach's notebook at the beginning of a period where the depth of England's next generation will be assessed.

Rankin, who has spent much of his county career under Giles at Warwickshire, overcame his early waywardness in Malahide with the scalps of Paul Stirling and Ed Joyce, then later in the innings he removed William Porterfield and Jonny Mooney to earn him the best figures of a bowler on England debut since Chris Tremlett's 4 for 32 against Bangladesh in 2005.

He formed a tall opening attack with Steven Finn which is likely to be the combination used for most of the series against Australia with England having rested James Anderson and Stuart Broad alongside the injury-enforced absence of Tim Bresnan. His chances of breaking into England's Ashes party for the Test series in Australia this winter are already being talked up.

Giles told ESPNcricinfo that the nerves had been evident. "All credit to him. He was probably more nervous yesterday than if he'd been playing against Australia," he said, "with him going home and all the talk around the Irish players playing for England. His first couple of overs were a bit nervous but he settled very quickly. To finish with four: what a great debut. He'll take that confidence into the next match."

Rankin and Finn were the only two frontline quicks selected against Ireland - Jamie Overton and Chris Jordan were overlooked - and for large chunks of the bowling performance England did feel a specialist bowler light, especially when Eoin Morgan turned to Michael Carberry's basic offspin. Giles, however, was impressed by the role of Ben Stokes who bowled for the first time in ODIs, ending with none for 51 in his 10 overs.

"Ben was our third seamer and his bowling has really developed over the last 12 months, and I thought he bowled pretty well yesterday. We have an inexperienced attack for these one-dayers and it's going to be a steep learning curve. In terms of the balance it was great to look down and see Stokes at No. 8, and at one point it looked as though we might need it. I think we are lucky in his case as he's a genuine allrounder and can fill two spots."

Giles was alluding to England's top order collapse as they slipped to 48 for 4 chasing 270 before being rescued by a world-record fifth wicket stand 220 between Eoin Morgan and Ravi Bopara. Although Giles would have preferred not to see the team in such a tricky position he believes they could yet feel the benefit of it further down the line.

"It was a very useful exercise. Obviously there are areas we can work on. Ireland setting us a challenging target was, in hindsight, good for the side because it put them under pressure. It was a bit closer than we'd have liked to be at one stage but overall for us to firstly see some of those guys in an international environment, and then for Morgan and Bopara to get us home was extremely worthwhile."

The side that faced Ireland resembled more a Lions team that a full England one-day side and although three players - Kevin Pietersen, Joe Root and Jonathan Trott - return to face Australia the bowling will retain a callow feel for the five-match series.

Giles has not been able to able to pick a full strength team during his time as one-day coach (Pietersen was injured for the Champions Trophy) but acknowledges the need for rotation and also sees the benefit of judging different players under the pressure of one-day cricket.

"Myself and Andy Flower, in our conversations, have always accepted that this would have to happen to manage the player workloads. We want to keep their services for the long-term. In the Champions Trophy we had our No 1 side out, barring Kevin Pietersen and that's our aim: to have our best sides available for the key tournaments.

"Between times we are going to have to rest and rotate. It does give us a chance to look at some of the young talent coming through, particularly with an eye on 2015 World Cup. We could say our best team - the one that played the Champions Trophy plus Kevin Pietersen - could get us to the World Cup. It might be, but it might not be and some of youngsters might be needed."

And he insists the split coaching roles which have been in place since January are dovetailing effectively. "It's going pretty smoothly. Myself and Andy have a good relationship. I feel, and I hope Andy feels the same, that we can talk about where we are and what we want. I'm looking at the one-day squad then have to take into account what Andy wants for the Test team. We certainly haven't had any fallings out."

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Andrew McGlashan is an assistant editor at ESPNcricinfo