Sir Alex Ferguson was angry with Manchester United even when they were 12 points clear at the top of the Premier League, according to former striker Robin van Persie.

Van Persie, who now plays for Fenerbahce, recalled an incident which took place in April 2013, during a season when United went on to become runaway champions. United had just played local rivals Manchester City -- who finished the season in second place -- and the home team lost 2-1 at Old Trafford.

That meant the lead at the top of the table for Ferguson's men was cut from 15 points to 12 points, upsetting the two-time European Cup winning manager. Sergio Aguero scored a late winning goal for City in a bad-tempered game, which saw eight players booked.

"We could have gone 18 points clear but still we were in a very good position. He was very hard on us, very angry," Van Persie told UEFA.

"He made everyone aware that everybody had to give their all. The training was very hard that week. He was almost punishing us. But that showed me he was a really good manager."