Spagnuolo was originally contracted to United for next season but after approaching his club they agreed to let him off the final year of his contract.
Spagnuolo told tribalfootball.com, “After having such a great season last year it has been really difficult being used so sparingly this season.
“I think Viddie (coach Aurelio Vidmar) is a great coach and his success in the Asian Champions League is testament to what Viddie has done for the Club. But I am in my mid 20s and I do not want to be used off the bench.
“It is every coach’s prerogative to play the players they want. I have no grudge against Viddie or the lub, they are great!.
“I need to move on and get out of my comfort zone in Adelaide.
“I have been talking about this for many months with my agent Lou and a few days ago I asked him to contact the club.
“He spoke to Michael Petrillo and the club agreed to my request. It makes me a bit nervous in that I do not know where my next deal will come from but it also makes me hungry and desperate to play every game for Adelaide United in the remainder of this season.
“I will miss everyone at this club and of course all my family and friends in Adelaide but some players leave their homes at 15 to travel to the other side of the world so really at my age I have to do it.
“I know I will come back to Adelaide at some point, just as Iain Fyfe has done by signing yesterday with Adelaide United.
“Now I want to finish off by winning the A-League and also doing well for the club at the Club World Championships if we get over the qualifying game.”