Duncan Fletcher fears Kevin Pietersen will struggle to cope with the demands of captaining England.
Former England coach Fletcher was surprised that the national selectors chose Pietersen to replace Michael Vaughan and Paul Collingwood as Test and one-day skipper because he has so little experience of leading a team.
The South Africa-born batsman has only taken charge of a single one-day international against New Zealand earlier this year and he will be thrown in at the deep end in Thursday's final Test against rampant South Africa.
Fletcher is concerned that Pietersen's batting will suffer as he tries to balance his team responsibilities with looking after his own form.
"I was a little bit surprised when the name of Kevin Pietersen came up to captain England," Fletcher told Sky Sports News. "It is from the point of view that he has not really been playing for England for long, and secondly he has no experience - which is crucial.
"You have to have some experience of captaincy," he told Sky Sports News.
"But the most important reason which really concerns me is what effect the captaincy will have on his batting - because they definitely need him very badly to perform as a batter.
"It could be very difficult if he is affected by the captaincy in a very big way."
Fletcher believes Middlesex opener Andrew Strauss would have been a better choice even though he has been out of favour in the one-day team since the 2007 World Cup.
"I would have put Andrew Strauss in as captain," he added. "I would have said for the moment 'put him in the one-day game'."