The move, effective immediately, comes just one day after FFA announced changes to the Player Contract Regulations which enable loans of Australian U23 players between A-League clubs.

It brings to an end a protracted stand off between the Central Coast Mariners and the 21-year-old midfielder who was a no-show at Mariners pre-season training sessions.

De Silva is Sydney coach Steve Corica’s second new signing since taking charge of the Sky Blues and underscores the new direction of the club to promote young talent.

     More: A-League introduces intra-league loans     

“Danny is a great signing for us, as there were a number of other A-League clubs who wanted him,” Corica said.

“He is a quality young player who will benefit and learn from the talent we have at the club already, and I think we will see the best of him this season.

“He improves our squad and is another dangerous, young, attack-minded midfielder for our Members to get excited about.”

    All the A-League off-season player moves    

No loan fees are permitted in relation to Intra-League Loans and De Silva will not be eligible to play against the Mariners.

But the youth international clearly wanted out of the Gosford outfit following the departure of coach Paul Okon towards the end of last season.

“This is a massive move for me and I’m eager to learn and improve with the excellent squad at Sydney FC, and also looking forward to joining the renown winning culture at the club,” De Silva said.

“I want to win trophies and do it playing the type of exciting football the Sydney FC members expect to see.

“I’m also looking forward to playing and working under Steve Corica too.  Everything he has had to say about the club and the way he intends to play excites me. I can’t wait to join the boys and get training ahead of the new season.”

De Silva will make his Sky Blues debut tonight in a pre-season friendly.

He first burst onto the scene as a 15-year old making his A-League debut for Perth Glory against Sydney FC in 2013, before a big money transfer to Roma two years later.

The Perth born youngster was loaned to Dutch club Roda JC where he made a number of appearances in the Eredivisie before returning to the A-League last season to play for Central Coast Mariners, winning the club’s supporters’ player of the season.

De Silva has been a regular throughout the Socceroos national youth teams and was called into the initial Socceroos squad for the 2015 Asian Cup.

Under the ‘Intra-League Loans’ framework, A-League clubs will be permitted to loan in, or out, a maximum of two players at any one time from the 2018/19 season onwards.

Loans may occur for either the whole season, or from ‘window to window’ in line with Australia’s FIFA Transfer Window calendar.

Crucially, the loan term for the 2018/19 season cannot exceed 31 May 2019, and players cannot be recalled to their parent club during the period of the loan agreement.