Despite twice finding themselves two goals behind, the Toffeemen launched a late fightback that allowed them to claim a momentous 4-4 draw at Old Trafford.
With Liverpool losing on home soil again, the result allowed Everton to consolidate seventh spot and keep them on target to finish above their great rivals in the table for the first time since 2005.
Yet that achievement will have a hollow feel because it will be Liverpool who contest the FA Cup final against Chelsea at Wembley on May 5 after the Reds secured Merseyside bragging rights last weekend.
"Last week was difficult," the Belgian told www.evertonfc.com.
"But if the team played against Liverpool like they did against United we could have won.
"Last week, in the first half we played well, but we had no energy in the second and no fight to win."
Fellaini gained due reward for his impressive contribution when he volleyed home Everton's second goal.
The Belgian also set up Steven Pienaar for the dramatic equaliser, with Nikica Jelavic adding to his impressive reputation by scoring twice, taking his overall tally to eight goals in 12 games since his £5.5million move to Goodison Park from Rangers in January.
"Niki has come in and done absolutely brilliantly for us," said full-back Tony Hibbert.
"If we put balls into the box, now both he and Marouane can get on the end of them, and they did."
Hibbert also had words of praise for Sylvain Distin, who was responsible for the defensive blunder that offered Liverpool a way back into the FA Cup tie, but responded with a superb performance at left-back as he neutralised the threat of Antonio Valencia.
"Sylvain was outstanding," said Hibbert.
"It's not natural for him to be out there but he coped with it well.
"Valencia is strong and quick, no-one would want to come up against him. But Sylvain stood strong."