Joe Denly must prove he is worth a place in England's World Cup plans after England head coach Trevor Bayliss revealed Liam Dawson has a chance taking his place in the final squad.

Denly pipped the slow left-armer to win a spot in England's preliminary squad last month and has played in the first two games of the summer, wins over Ireland in Malahide and in a one-off Twenty20 against Pakistan on Sunday.

The Kent all-rounder looked to have timed his run to perfection after almost a decade in the international wilderness but while selectors value his versatile batting, uncertainty over his late-blooming leg spin could yet force a change of heart.

Moeen Ali's rib injury means Denly will play the role of spin bowling all-rounder at the Oval on Wednesday, the first of five one-day internationals against Pakistan before the final 15 is revealed, and needs to impress with the ball.

The first two deliveries of his only over in Cardiff were long hops that Babar Azam hammered for six and Bayliss cranked up the pressure on the eve of the series by admitting Dawson was now under active consideration by selectors.

"He's not the only bowler to run in and bowl a couple half-volleys to start a spell, (but) it's an interesting position, that one," he said.

"Someone like Dawson will certainly be in discussions. He's done well this year and he's done well for us in the past when he's been given an opportunity at this level. It's getting to the business end.

"It's this 17 and Dawson, I don't think it would be out of place in saying it's probably down to that 18. I think the final 15 would come from that."

Dawson played the last of his three ODIs against Sri Lanka at Dambulla in October but an impressive winter on the franchise circuit and a strong start to the season with Hampshire has brought him back to the fore. The slow left-armer even looks set to join up with the team before the Pakistan series concludes.

"We actually spoke about that if Mo didn't play this first match but we've decided to give Denly a go this time," added Bayliss.

"There will be a little bit of flexibility and I am sure there will be discussions ongoing throughout this series."

There will also be another outing for Dawson's county captain James Vince at the top of the order, with first-choice opener Jason Roy not being risked after recent back spasms. Seamer Mark Wood is also being carefully managed due to his ongoing ankle complaint.

"If it was an important game and we really needed them to play, they would be playing, but there's no real need," was Bayliss' verdict.

"We're playing a little bit safe but it also gives us the chance to play some of the bench strength."

The Australian also spoke for the first time on Alex Hales, who was discarded from the pre-World Cup training camp after news broke that he had failed two tests for recreational drugs.

Captain Eoin Morgan said the issue led to a "complete breakdown in trust", with Bayliss at a loss to explain the player's timing.

"I never had the chance to (play at a World Cup), nowhere near. I can't imagine throwing it away," he said.

"He might argue, but it is a message to everyone else out there that those days are over. You can still go out and have a few beers and enjoy yourselves, but it's about making the right decisions and choices. Everyone is more than capable of making those right decisions."