Joe Root can match world's best Kohli, Smith; Buttler excellent for captaincy: Warne

London: Shane Warne believes England should seriously consider replacing Joe Root with Jos Buttler as Test captain to allow Root to focus on becoming the world's best batsman.

Australia spin great Warne says the Yorkshire star could dominate the global game with the bat and feels Buttler would make a "very, very good" Test skipper.

Warne worked with Buttler in his role as mentor for Indian Premier League team Rajasthan Royals and is convinced the Lancashire player has credible Test leadership skills.

"I've worked with Jos a bit this year, and I think he's someone who would make an excellent captain," said Warne. "I really enjoyed working with him, I'd like to think I helped him out a little bit."

Warne, who is promoting his autobiography, said Root is England's best player but would be disappointed with his conversion rate when it came to hundreds.

"He'd love to have more hundreds to be able to be spoken about in the same sentences as Virat Kohli and Steve Smith," he said.

"Maybe England could think about their best player having the shackles off, not having the responsibility of captaincy, and give it to someone like Jos Buttler," he added.

"If he (Root) totally 100 percent concentrates on his cricket, his batting and nothing else, then maybe we might see Joe Root become the best batsman in the world," Warne said. "He's got the talent to do it."