Duncan Fletcher has warned against making Kevin Pietersen England's permanent one-day captain.
Fletcher, who was Peter Moores' predecessor as England coach, is worried that the extra leadership responsibility would have a detrimental impact on Pietersen's batting.
The South African-born batsman led his adopted country for the first time during the 51-run defeat to New Zealand on Saturday.
He was given the chance because of regular skipper Paul Collingwood's four-match ban for presiding over a slow over-rate during the fourth match of the series, his second offence in the last 12 months.
"I'm not sure if Kevin Pietersen should be captain at this stage of his career," Fletcher wrote in his Guardian column on Monday.
"He's a free spirit - just look at that superb switch-hit at Chester-le-Street - and I'm worried the added pressures of leadership will affect the way he bats.
"For me, Andrew Strauss should have been picked and should have been captain."
Fletcher returned to one of his favourite themes by placing the blame for England's 3-1 NatWest Series defeat squarely at the door of the county game.
The Zimbabwean was noted during his eight-year tenure for allowing his centrally-contracted players little opportunity to take part in domestic cricket.
Instead, he prescribed rest and practice time between Test and one-day international exertions - a formula largely abandoned by Moores.
"The bowlers should be blamed for what happened, but the problem goes deeper than a few wayward deliveries," he added.
"I'll say it until I'm blue in the face: it all goes back to county level.
"How much has county cricket really taught these guys? How much are they practising in the nets? The answer is not a lot, because there is simply no time to have nets.
"England also need someone in there with the raw pace to blast batters out, but a guy like Sajid Mahmood is getting lost in the system."