The powerful Perth-born centre-back has joined the A-League outfit following his move from South Korean top flight side Jeonnam Dragons, where he made 49 appearances.
Mrcela has been a regular fixture in the heart of the defence for the Dragons since 2016 where his physical presence and aerial prowess proved a great asset.
The 27-year-old said he's excited at the prospect of playing under newly appointed coach Tony Popovic .
"I'm a defender and Popovic was a world class defender in his day. He was in the Socceroos and in the Premier League, so I can learn a lot from him," he said.

"Popovic is a winner, we all know that, and I want to win things for this club and that's why I'm here, for that challenge.

"I can't wait to play in front of my friends and family here, hopefully there will be a few members added to the club now."

Mrcela moved to Croatia with his family in 1996 before joining the RNK Split Academy side in 2001. He spent eight years in Split, before making the transition to First Team football in the Croatian lower leagues.

Following a season each at Imotski (loan), Mosor, Hrvatski Dragovoljac and two seasons with Zagreb-based side Lokomotiva, where he gained Europa League experience, Mrcela decided it was time for a change and moved to the K-League.
Newly appointed Assistant Coach Hayden Foxe said Mrcela’s best years are ahead of him.

“We’ve signed him at the prime time of his career,” Foxe said. “He’s a fantastic professional who works extremely hard and is greatly experienced having played in Europe for over a decade."