Redknapp feared hair would get in Bale's way
Real Madrid's Welsh striker Gareth Bale celebrates after scoring during the Spanish La Liga match against Villarreal at El Madrigal Stadium in Villareal on September 14, 2013
Bale left Tottenham for Real Madrid last month for a reported world-record transfer fee of £85 million ($137 million, 100 million euros), but Redknapp says he used to have doubts about the Welsh forward's strength of character.
"He drove me mad in training," wrote Redknapp in his autobiography, which is being serialised in British newspaper the Daily Mail.
"Technically, he was outstanding, but he always seemed to be playing with his hair.
"It was never right. He'd be flicking the fringe or wiping it out of his eyes and I would be going quietly mad, just watching. 'Gareth, leave your barnet alone! Gareth! Stop touching you hair!'"
'Barnet' is cockney rhyming slang for 'hair', derived from a rhyme with 'Barnet Fair'.
Redknapp, who now manages second-tier Queens Park Rangers, was also worried about Bale's propensity for injury.
"He was always getting a little knock in training, too. He'd go down then limp off and I always thought the physios made too much fuss of him," he said.
"It was the same pattern every morning. Gareth would tumble and stay there, and they'd all go running over. In the end I told them just to leave him alone."