The Ashes: Joe Root's Progress Impresses Alastair Cook

England captain Alastair Cook has never seen a player improve as much in a short space of time as star batsman Joe Root.(Joe Root Rises to No. 1)

The 24-year-old Yorkshireman, regarded as a captain in waiting, has scored England's only two hundreds of the ongoing Ashes series to help put his side an unbeatable 3-1 up against Australia heading into Thursday's fifth and final Test at The Oval.

Such has been Root's form during the past two months, he has displaced Australia's Steven Smith at the top of the International Cricket Council's Test batting rankings, with England paceman Stuart Broad now his main rival for man-of-the-series honours in the Ashes.(Joe Root Banned From Celebrating)

"He's improved leaps and bounds," opening batsman Cook said on Wednesday of Root, who has often come to the crease after a top-order collapse.

"I've never seen a player improve like that."(Joe Root Leaves Australian Bowlers With no Margin for Error)

Cook said Root's style was similar to that of New Zealand rising star Kane Williamson, who has also played for Yorkshire and was lauded earlier this season by the county's former England opening batsman Geoffrey Boycott as someone good enough to have played on uncovered pitches.

"It reminds me a little bit of Kane Williamson. Those two are very classical players . . . you watch them play a Twenty20 knock or (in) a Test match and they're still doing very similar things.

"That's a huge credit to Joe. It's a pleasure to watch him."

Meanwhile, Cook said a more positive approach had helped his side neutralise the impact of Australia fast bowler Mitchell Johnson, although he accepted local conditions had played their part as well.

Left-arm quick Johnson took a remarkable 37 wickets at under 14 apiece during Australia's 5-0 home whitewash of England in the 2013/14 Ashes.

But so far this series he has been restricted to 11 wickets in four Tests, although having to defend low totals -- including Australia's 60 all out in the first innings of their fourth Test defeat at Trent Bridge -- did not help his cause.

"We've played him a bit better," Cook said. "On the whole, we've played all their bowlers pretty well -- and we've scored at a good rate.

"They haven't managed to tie us down as well as we've managed to do with them," he added.

Cook said England should not be swept up in Ashes euphoria, with stern tests set to come on tours of the UAE and South Africa later this year.

"We've got to be really careful that we don't get too carried away.

"We've got Abu Dhabi, where I don't think anyone has won against Pakistan, and South Africa to come. I do feel we're very well-equipped to go to those places.

"Whether we win or lose, I've seen enough from the players and the balance of the squad (to be confident of our ability) to do very well in both places."

"It does make me laugh that the Ashes, win or lose, is the barometer of how healthy or unhealthy your whole system is."

Cook, as he did after the fourth Test, again praised outgoing Australia captain Michael Clarke, who will retire from international duty after The Oval match.

Asked if the team would have any specific plans, such as a guard of honour, for Clarke at the south London ground, Cook laughingly said: "Hopefully, not half-volleys.

"Michael has been a wonderful cricketer for Australia and, hopefully, he'll be remembered for all the right reasons.

"Australia will miss a mighty fine batsman and a very good captain."