Former Manchester United manager Alex Ferguson joked on Monday that Anthony Martial's explosive start to life in English football proved the club were right to break the bank for him.

United reportedly paid an initial fee of £36 million ($55 million, 49 million euros) to Monaco for the 19-year-old French striker, which it is thought could rise to £58 million.

United manager Louis van Gaal said the price was "ridiculous", but with Martial having netted three times in his first two league games -- including a fine debut goal against Liverpool -- Ferguson feels he is proving his worth.

Asked at an event to promote his new book, 'Leading', Ferguson, who retired in 2013, was asked if the fee United had paid for Martial was ridiculous and replied: "Not at the moment it's not!"