Refreshed England captain Joe Root says it's "just a matter of time" before he eliminates one of the few flaws in his game - an inability to convert fifties into hundreds.

Root's low conversion rate in Test matches has long been a talking point surrounding the England star and one of the reasons his career record is one rung below those of batting contemporaries Virat Kohli, Steve Smith and Kane Williamson.

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Kohli's record of 21 centuries and 16 fifties - a conversion rate of 56.76 per cent - is among the best in the game's history, while Smith (48.94 per cent) and Williamson (40.91 per cent) are also well ahead of Root, who has 13 hundreds and 39 fifties (25 per cent).

The right-hander has previously expressed his frustration at the trend and acknowledges that turning half-centuries into three-figure scores can often be the difference between winning and losing Test matches.

But the 27-year-old is confident he can reverse the trend.

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"It can change very quickly," he told Sky Sports ahead of the first Test against Pakistan, starting on Thursday.

"I've got to keep trusting in my own game and making sure that I'm constantly trying to evolve and get better, but also have the same mental approach that I have because I have been very consistent with the bat.

"I'm sure it's just a matter of time and there will be one or two innings where it just clicks into place and I'll go on a little run of big scores. I've just got to keep searching for it, trusting it and believing it and I know eventually it will happen.

"When you're losing it is very hard because you look at that and you think sometimes the difference is going on and making big hundreds.

"One thing I will say is that if I keep getting up and beyond fifty and I start going on a bit more frequently then we'll be in a strong place as a side and I'll be scoring a lot more runs."

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Root's consistency and inability to push on to big scores was underlined last year when he scored a fifty in his 12th consecutive Test, equalling the record of South African AB de Villiers, but turned only three of them into hundreds.

And the trend continued during England's winter tour of Australia and New Zealand, when he scored seven fifties in as many Tests but managed a highest score of 83.

Captain Root passes fifty but fails to push on again

It's a problem that has only begun in recent years; it took Root 50 Test innings to score his seventh Test hundred (alongside 13 fifties) but his next six Test tons have taken him 74 innings and come alongside 28 half-centuries.

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Speaking last year, former England captain Ian Botham said the issue may have become so big that Root was trying too hard to eradicate it.

"I can tell you now it drives him mad, he's very conscious of that," Botham said.

"I just wonder if he's now so conscious of it that he actually tries too hard, whether that's the case I don't know."

Conversion Rates of ICC's Top 10 Ranked Test Batsmen

100s/50s (conversion percentage)

Steve Smith - 23/24 (49 per cent)

Virat Kohli - 21/16 (57 per cent)

Joe Root - 13/39 (25 per cent)

Kane Williamson - 18/26 (41 per cent)

David Warner - 21/29 (42 per cent)

AB de Villiers - 22/46 (32 per cent)

Cheteshwar Pujara - 14/17 (45 per cent)

Dean Elgar - 11/12 (48 per cent)

Aiden Markram - 4/3 (57 per cent)

Hashim Amla - 28/39 (42 per cent)