The Ivory Coast star announced he was ending his eight-year association with the Blues shortly after spurring them on to UEFA Champions League success in May.

Drogba went on to sign for Chinese Super League outfit Shanghai Shenhua, where he links up with former Stamford Bridge striking partner Nicolas Anelka.

Ferguson believes the 34-year-old striker was such an integral part of the set-up at the west London club due to his phenomenal goal-scoring record in important games that his departure will have weakened one of United's main title rivals.

Drogba not only scored the crucial equaliser in the Champions League final against Bayern Munich and the winning penalty in the subsequent shoot-out, he also grabbed the winner in the FA Cup final victory over Liverpool.

"When you think of the season he's just had, I must say it is a big boost for us that Drogba is leaving Chelsea," Ferguson said in The People.

"He scored that fantastic goal in the final with two minutes to go and his goalscoring record in the big games, in big finals, is incredible.

"As far as I was concerned, he won the Champions League for Chelsea."