Necevski, who has been demoted to number two behind Clint Bolton in the early stages of the season, believes the former Wigan Athletic shot-stopper has been an invaluable asset to the club, especially during this year's pre-season.
"John has been absolutely massive for me and I know it's the same for Clint," Necevski said.
"I remember watching him play in the old state league when I was 12 or 13 and then followed his career over in the English Premier League."
39-year old Filan enjoyed a lengthy stint playing in England, beginning with Cambridge United in 1993 before moving onto Nottingham Forest (loan), Coventry City, Blackburn Rovers, Wigan and Doncaster Rovers (loan), and Necevski said his standing in the game has assisted his development greatly.
"It's huge to have someone of his stature and experience at the club who can ultimately help us as keepers and us as a club to win a championship with Sydney FC," Necevski added.