The previous week the Belgium international was booed off in the FA Cup quarter-final defeat to Wigan and there has been speculation all season about his future at the club.
However, Jagielka, himself currently sidelined by injury, insists there should be no doubts about 25-year-old Fellaini's determination to do his best for the Toffees.
"He had a painful ankle problem before the City game and he could have milked it and missed the game before disappearing off on international week but he was desperate to play," he told the Liverpool Echo.
"He strapped himself up and put in a great performance. You cannot question his commitment.
"Felli has taken all the beatings for us throughout the season and he will feel sometimes like the world is against him. Sometimes it has been.
"You can forget he is not that old. He hasn't grown up in the Premier League for all his career and hasn't been at this level as long as others."