England have made one tough call for the must-win Sharjah Test, but will leave a potentially even trickier one until the last minute.

Alastair Cook admits it was "not much fun" having to tell out-of-form wicketkeeper Jos Buttler he was being dropped as England try to battle back for a 1-1 series draw in the final match of three.

More enjoyable was informing James Taylor he will finally get another chance in England's middle order - more than three years after he was cast aside following two Tests against South Africa.

But Cook and coach Trevor Bayliss must still decided whether they bring in a like-for-like replacement for rested seamer Mark Wood. Liam Plunkett is the obvious first port of call ahead of Chris Jordan - or they could take a punt on conditions and recall all-rounder Samit Patel as a third spin option.

The stakes are high, and it could become all too obvious very quickly if England go the wrong way at a noted spin-friendly venue.

In a series where the tourists' seamers have so far consistently outbowled spin twins Adil Rashid and Moeen Ali, Patel is still the left-field selection.

"That's the major decision we have to make," said Cook.

"It will be really easy after the game in hindsight to see whether we've made the right decision - but it will be a tough call."

Cook is much more convinced of Taylor's renewed credentials as a Test match batsman.

Asked if the 25-year-old is ready to return, he said: "I firmly believe he is.

"I'm sure he feels he was harshly treated ... sometimes that's the way of selection.

"(But) he's gone away over the last three years, and he's a lot different player than what I remember him as.

"He's itching to play, and you don't average 47-48 in first-class cricket without being a fine player."

England have been persuaded by Taylor's adaptability against spin, and determination to make the most of an opportunity once he is set.

"One of his very strong points is that when he gets in he goes on to get big scores," added his captain.

"We know how important first-innings runs are to set the game up."

While Taylor comes back in from the cold, Buttler is at a career crossroads.

Jonny Bairstow will take over the gloves, with Buttler's absence opening up the place for Taylor in what will be a rejigged middle order below the prolific Joe Root at number four.

It fell to Cook, of course, to confirm to Buttler what he had surely already guessed after a miserable run of form with the bat.

"Telling him was part of the job that is not much fun," he said.

"He's clearly struggled for runs in the last six months or so.

"He'll have to go away and be really clear on how he wants to play in Test cricket.

"He knows his game really well in Twenty20 and one-day cricket, but he probably knows it less well Test cricket.

"It's about finding his ideal method and sticking by that."

Cook suggested Buttler could do worse than following the example set by Root, who was dropped after the 2013/14 Ashes but now sits atop the global Test batting rankings.

"We all know the amount of talent (Jos) has got - you see him play an innings that everyone around the world says is amazing - but he's not the first person who has come in, done pretty well then had a tough patch, been left out and come back stronger," Cook said.

"He only has to look at Joe, getting left out of that Sydney game and using it as motivation to be clear on how he wanted to play in every situation.

"He's come back as a far better player because of it."