Alessandro Del Piero is irreplaceable, Graham Arnold says, but the new Sydney FC coach has vowed to bring a similarly good player to the A-League club.

Arnold on Thursday was unveiled as Sydney's eighth coach in nine seasons, with the former Central Coast mentor saying his three-year deal was a "dream come true".

The former Socceroos' coach replaces Frank Farina, who was sacked barely two weeks ago after failing to get the club beyond the opening week of the A-League finals.

Arnold prided himself on winning the championship and minor premiership during his three seasons at the cash-strapped Mariners without a big-name marquee player.

He now says he's excited to be at a club where he will have a chequebook at his disposal.