Manchester United won the match 2-1 in London, after an late goal by winger Cristiano Ronaldo.
Ferguson said: “I must say that was the most difficult game we have had all season.
“I think it is a significant result, pariticularly scoring late on.
“Ronaldo just kept going and deserved to get the man of the match.
“Credit to Fulham, they never gave use a moment to settle. Fulham will feel very aggrieved with the result.”