Trevor Bayliss has hinted England may "have a decision to make" over Jonny Bairstow's future as Test wicketkeeper. Bairstow fractured a finger while taking a catch behind the stumps at Trent Bridge and is a doubt for the fourth Test, starting next week; if passed fit, he is likely to play as a specialist batsman only.

Bairstow's injury enabled Jos Buttler - England's regular limited-overs keeper - to retake the gloves for the first time in Tests since 2015. Buttler subsequently scored his maiden Test hundred, and he seems set to have a chance to stake a permanent claim for the wicketkeeper's role, a change that could allow Bairstow to fill one of England's problem batting positions higher up the order.

Bairstow has long been adamant that he wants to continue keeping wicket, and has made significant improvements since first stepping in as Matt Prior's replacement on the 2013-14 Ashes tour. However, Bayliss, England's coach, suggested that while "convincing Jonny" of the merits of a switch might prove difficult, it was in Buttler's hands to make the most of the opportunity.

"I think keeping in the next game will probably be the most difficult [for Bairstow]," he said. "We've got to check with the medical guys in the next few days. They are suggesting he may not be able to keep but might be able to bat. We'll have to see how it responds. If that gives someone else another opportunity - it's like any injury, if someone comes in and does well, then you have a decision to make.

"That'll be the hard thing, trying to convince Jonny. That will be a decision that is taken from the team point of view. He is a world-class batter, we know that, one of the difficult things might be convincing Jonny of that. I think he has improved his keeping over the last couple of years from where he was say when we were in South Africa. He's aware of that. He's done some hard work. Jos will have to do some hard work as well. He's been keeping a lot in one-day cricket but keeping 100 overs-a-day can be difficult, day after day, Test after Test. There are other options out there as well."

While Bairstow has made a strong case as a wicketkeeper-batsman - he averages 42.33 with the gloves as opposed to 38.55 overall - there remains a school of thought that he could be even more productive. Freed from keeping, Bairstow could potentially bat as high as No. 4, a position which has been problematic since Joe Root moved up to bat at No. 3. Perhaps significantly, Bairstow has averaged more than 50 in the ODI side over the last year, playing solely as a batsman - and Bayliss said he was not worried that a change in roles would affect his output in Tests.

"If that was the way we went, it would certainly be a deep conversation," Bayliss said. "Jonny's a reasonable bloke. If that's the way we wanted to go… in the long run, he wants to play Test cricket. We know he wants to keep but there would be a lot of explaining and chatting."

Should Bairstow be able to play as a batsman in the Southampton Test, there may be another benefit in allowing Ollie Pope to shift down the order. Pope, 20, made his debut in the second Test and has so far made 54 runs in three innings batting at No. 4 - despite having no previous experience in that position in a career spanning 15 first-class matches.

"He's batted no higher than six for Surrey so it was a big ask to come into international cricket and bat four but the short times he's been at the crease showed that he might be a good international cricketer," Bayliss said. "We would have probably liked to have started him off down a bit lower but the hole was at No. 4. Obviously, Jonny is an option there as well which might allow Ollie to drop a little lower. These are all things we've discussed."

Pressure has also been building on Alastair Cook, with England's leading Test run-scorer having not gone past 29 in five innings against India. Root indicated after the defeat at Trent Bridge that Cook retained his full backing, and Bayliss suggested that he was not so much out of form as "out of runs".

"Cooky has not changed his demeanour. You wouldn't know there was any difference between now and when he is scoring plenty of runs. He still practises as hard, if not harder, than anyone else. You watch him play in the nets and he is actually striking the ball quite nicely. His feet move well. I wouldn't say he is out of form - he is still hitting the ball well - he is out of runs in the middle. But he is giving himself every opportunity. He practises hard and he still plays an active role in his position in the team."