Sir Alex Ferguson admits his tough approach to discipline could have cost him Premier League titles during his time at Manchester United.
Ferguson, who won 13 league titles at United, had a number of high-profile bust-ups with some of the best players in the world during his 27-year tenure at Old Trafford.
David Beckham, Roy Keane, Jaap Stam and Ruud Van Nistelrooy – among others – incurred the Scot's wrath during his trophy-laden spell at the club.
Ferguson says he has no regrets about taking a hardline approach with his players, but admits the policy may have cost him silverware.
"People will give a manager plenty of opportunities to crack the whip so it's best to pick and choose your moments," the former United manager writes in his new book Leading, which is out on October 6.
"You don't have to dish out a punishment very often before everyone gets the message.
"I place discipline above all else and it might have cost us several titles.
"But if I had to repeat things I'd do it precisely the same because discipline has to come before anything else."
The three major bust-ups Ferguson could be alluding in his book extract, which was published on Manchester United's Facebook page on Thursday morning, concern Paul Ince, Stam and Keane.
Ferguson clashed with Ince during the 94-95 season, when United failed to win the title, referring to him as a "bottler" and a "big-time Charlie".
The ruthless disposal of Stam also came during a trophyless year for the Scot.
At the start of the 2001-2 season, Ferguson became enraged with Stam over details which were published in his autobiography.
The Dutch defender claimed that Ferguson made an illegal approach to sign him when he was at PSV Eindhoven. The center-back also wrote about his team-mates in the publication, called Head to Head.
Despite being a rock at the heart of the United defense for the past three years, Ferguson sold Stam to Lazio and replaced him with 35-year-old Frenchman Laurent Blanc instead.
United came second by eight points to Chelsea in 2005-06, when he clashed with Keane and Ruud van Nistelrooy.
Despite being one of the most prolific scorers in the club's recent history, Van Nistelrooy started just five more United games after the League Cup final, when he swore at Ferguson after he informed him he would not be bringing him off the bench for the final at the Millennium Stadium in Cardiff.
The striker was sold to Real Madrid that summer.
Keane was also famously jettisoned at the start of that season after criticizing his team-mates during an interview for the club's in-house TV station.
Comparisons have been drawn between Ferguson's hardline approach and that of current manager Louis van Gaal.
The Dutchman is something of a disciplinarian, and he failed to win a trophy during his first year at the club.
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