Joe Root's prodigious batting could reach a new level if he is made England captain, Alastair Cook said after stepping down from the role following 4-1/2 years in charge.

The 26-year-old Root, the world's third-ranked batsman, is favourite to be named as Cook's successor, raising some concerns that the extra responsibility could affect his form.

Cook, who captained England for a record 59 tests, sees no reason why the Yorkshireman woud not thrive -- pointing to the impact captaincy has had on India's run-machine Virat Kohli.

"He (Root) has got a very, very good cricket brain, he's a part of the newer generation of cricketers and he's a bloody good cricketer who demands respect in the dressing room because of that," Cook said. "I think he'll be an outstanding candidate.

"It's a valid argument (that his form could suffer) in one sense but it has driven the batting of others to another level.

"Virat Kohli for example has flourished, (Australia's) Steve Smith has flourished, (New Zealand's) Kane Williamson as well."

Cook, 32, was made permanent captain in 2012 and while he scored 10 of his record 30 test centuries in the role, he has only reached three figures five times in his last 48 tests.

A decision on who will replace Cook as test captain is expected within the next two weeks.

OBVIOUS CANDIDATE

Despite concerns about the possible impact the captaincy could have on Root, England bowler James Anderson believes he is the "obvious candidate" for the job.

"Root is fairly quiet but he has got that fire in his belly. He's a really impressive young man," Anderson told the BBC.

"Root gets into situations, one-on-ones, with people. He speaks a lot of sense when he does speak.

"He's the obvious candidate. The decision is a big one because he's our best player, so you obviously don't want that to be affected."

Root, who has scored 4,594 test runs since making his debut in 2012, has often been Cook's go-to man during matches, according to Anderson.

"In the brief period Alastair Cook's been off the field -- for bathroom breaks -- Root's been in there making changes. He's been good," he said.

England face a busy year with a home series against South Africa and West Indies followed by the Ashes at the end of 2017 in Australia.