England will persist with Jos Buttler as opener for Sunday afternoon's Twenty20 decider against South Africa at Centurion.

Buttler has partnered Jason Roy at the top of the order at East London and Durban but his recent lean spell in Tests has transferred to T20s and scores of 15 and two has led to speculation he could drop down to five or six.

There is a growing clamour for Jonny Bairstow to be bumped up one place so he and Roy can attempt a double act that has proven hugely successful in one-day internationals, where the pair have 11 century partnerships in 35 innings.

Their average of 67.51 is the highest from any opening combination with more than 1,000 ODI runs together but England will resist the temptation to unite the pair, keeping faith with Buttler.

The wicketkeeper-batsman is yet to make a half-century in any format this winter but three of his seven T20 fifties have come as an opener and he averages 40.14 there with a phenomenal strike rate of 156.98.

England captain Eoin Morgan is convinced the top-three in its current guise is the best option for England, whose dramatic two-run victory over the Proteas at Durban set up a winner-takes-all clash this weekend.

When asked whether he was contemplating moving Buttler down the order, Morgan replied: "Not for Sunday, definitely not.

"Jos is one of our greatest white-ball cricketers, as a batsman, never mind with the gloves.

"We believe him, Jason and Jonny are our top-three at the moment, moving forward."

Buttler's reputation as an outstanding 'finisher' in limited-overs cricket has been well-established but Moeen Ali believes his team-mate is more than capable of thriving wherever he bats.

Moeen said: "The lucky thing is that we can change it and we'd be just as strong or even stronger.

"Jos is brilliant at number five but he's also brilliant when he opens. So sometimes when he bats at five and plays the way he does, people say he could open and bat like that and bat for longer.

"Jos is one of our best finishers but we as a five, six, seven, eight have to get better as well. We can't just rely on him. If he comes off at the top, we win the game in 10 overs."

With England steadfast about where Buttler will bat at Supersport Park, Dawid Malan is once again likely to miss out despite averaging 57.25 with a strike-rate of 156.31 in nine T20 internationals.

Pressure is on Joe Denly's shoulders after the Kent batsman was dismissed for one on Friday evening, the seventh time in 11 T20 innings for England where he has failed to make it to double figures.

However, England could be unchanged for the third game in a row as they target a fifth successive bilateral T20 series victory to lay down a marker for this year's World Cup in Australia.