England have given the clearest indication yet that Joe Root, rather than Nick Compton, will open the batting with Alastair Cook during the Ashes. Root will move up the order for the warm-up match against Essex beginning on Sunday, with Compton omitted from the squad and Geoff Miller, the national selector, describing Root as "currently the best opening partner" for Cook.

Compton has paid the price for a disappointing series against New Zealand in May. He looked devoid of confidence in scoring 39 runs in four innings while, in the second Test at Headingley, Root and Jonny Bairstow batted with admirable freedom in posting a partnership of 124 for the fifth wicket.

Root has continued to impress in almost every scenario with which he has been confronted. He has shown a welcome adaptability in limited-overs and Test cricket and, while it might be considered something of a risk to promote him to the top of the order for the first time in an Ashes Test, he has played most of his county cricket as an opening batsman at Yorkshire. The England management have recognised his calm temperament and skill and see him as a big part of the team's future in all formats.

"We believe Joe Root is currently the best opening partner for Alastair Cook and he will open the batting against Essex," Miller said. "Joe has performed well for Yorkshire at the top of the order earlier this season and during his international career so far has proven to be very adaptable in all three formats and relished the challenge of international cricket."

The ECB have announced a 14-man squad to play Essex, including Graeme Swann, who suffered a calf problem during the ICC Champions Trophy, and Kevin Pietersen for what will be only his second first-class appearance since England's tour of New Zealand in March. Boyd Rankin, the former Ireland fast bowler, has also been called up ahead of Chris Tremlett, after being added to both of England's limited-overs squads in the last month.

Compton might consider himself unfortunate to miss out. It is only four Tests since he was celebrating back-to-back centuries in the first two Tests in New Zealand in March while he responded to the challenge 'go back to county cricket and score some runs' by making 166 in his first innings back in Championship cricket against a strong Durham attack. The next highest score in the innings was 42.

He remains available for Somerset's tourist game against Australia from Wednesday - his 30th birthday - but it is now highly unlikely that he will feature in the first Investec Ashes Test which starts on July 10. England will use the Essex game not just for match practice, but to discuss plans and merge as a team. Compton's omission is a clear indication that the selectors have decided to move on. While continuity of selection has been a feature of England's success in recent years, the England management can still be ruthless when they deem it necessary.

The emergence of Bairstow is just as relevant to Compton's demotion as Root's elevation. Bairstow has been on the fringes of the side for some time and has impressed in his limited opportunities. He scored 149 in the final Test against South Africa in 2012 (95 in the first innings and 54 in the second) as well the impressive innings of 64 against New Zealand in Leeds. While Compton is admired for his fortitude and determination, Bairstow is seen as having the greater potential and the wider range of strokes with which to accelerate and hurt opposition bowling attacks. Aged 23, he also has greater scope for the future.

"This match is a vital part of our preparations for the Investec Ashes after a period of limited overs cricket for a large number of the squad," Miller said. "We have a very exciting two months of Test cricket coming up and it is important that we start well at Chelmsford next week. Kevin Pietersen has had no complications following his recent return to cricket after a knee injury which is pleasing and Graeme Swann is recovering well from a calf injury."

An England spokesman confirmed that the match against Essex will be a first-class encounter and so feature just 11 players on each team. The spokesman also confirmed that there are no plans to boost the Essex side with reinforcements. Essex, who currently occupy a mid-table position in Division Two of the County Championship, were recently bowled out for just 20 by Lancashire.

England squad: Alastair Cook (capt), James Anderson, Jonny Bairstow, Ian Bell, Tim Bresnan, Stuart Broad, Steven Finn, Graham Onions, Kevin Pietersen, Matt Prior, Boyd Rankin, Joe Root, Graeme Swann, Jonathan Trott