England coach Trevor Bayliss admits England's top order has been their Achilles heel "for the last six or seven years" but is hopeful World Cup winner Jason Roy can help provide a cure during the Ashes.

Bayliss has been trying to find a solution to the Test team's top-three woes throughout his four-year reign, which comes to an end in September, but has yet to uncover the answer.

Concerns spiked again after a wobbly start saw England bowled out for 85 on Wednesday in the first session of their inaugural match against Ireland.

The seamers went on to rescue the result, skittling the Irish for 38 on day three, but Bayliss left little doubt about where his worries lay heading into the Thursday's series opener against Australia.

Asked if the head of the innings was England's biggest problem, he responded: "You don't have to be Einstein to work that out.

"They have been for the last six or seven years, but it didn't stop us (winning the Ashes) four years ago."

Rory Burns, Jason Roy and Joe Denly have been retained for the first Test but all three head to Edgbaston with question marks over their Test pedigree.

Burns averages just 22.28 in seven appearances, with Denly only marginally better off on 24.16 in his three appearances.

Both face a battle to prove they have a future at the highest level, but it is World Cup winner Roy who probably has the highest ceiling of the trio.

He has established himself as one of the most dominant batsmen in one-day cricket and was crucial in setting the tone for England's triumphant campaign.

The 28-year-old's red-ball record for Surrey is less persuasive and by asking him to open England are making a call the county have shied away from, Roy having frequently batted in the middle order and only occasionally as a number three.

He hit 72 in his second Test innings against Ireland having been spared the new ball by nightwatchman Jack Leach, a higher score than either Burns or Denly have managed to date and on a pitch rated by captain Joe Root as "substandard".

"Like any debutant, he looked nervous but to score 70-odd in your first Test was a good effort," said Bayliss.

"There was a bit more in those wickets than I'm sure he's been used to in white-ball cricket over the last few years but runs are runs. He wouldn't be the first player to look scratchy and eke out runs. In fact, that's a good sign, I think.

"We want him to go out and play his natural game but in red-ball cricket you have to be a little more selective. You've got to make a conscious effort to say to yourself, 'I'm not going to go for the big cover drive on the up until I'm really settled, the wicket is flat or the ball's not doing as much'.

"Jason probably looked a little scratchy but he got 72 and helped us win the game."

Bayliss faces a big job managing his players in the coming weeks, with the emotional and physical demands of the World Cup campaign given just 10 days to dissipate before a hard-fought clash with the Irish and now the intensity of the Ashes around the corner.

"It would have been nice to have another week to let the World Cup soak in and take stock of it all," he conceded.

"It was two or three days and then you're back into thinking about planning another Test match.

"Hopefully over the next three or four days they have got the opportunity to get away from it and down tools for a while.

"But I don't think we'll have any problems getting up for the hype that's around the Ashes."