Just one week before the A-League season starts, the Wanderers will begin the search for a new coach for the first time in five years, after Popovic abruptly left the club on Sunday.

He will travel to Istanbul to finalise a transfer to the Super Lig club after reaching an agreement on personal terms and will complete formalities once he arrives in Turkey.

The timing of Popovic's departure has left the club's preparations for the new season in tatters. It follows an off-season in which the Western Sydney board approved unprecedented spending on player signings and salaries, as Popovic moulded a squad to his requirements, in hopes of finally winning the A-League title.

Chief executive John Tsatsimas admits the club faces a major headache to ensure that the spending will still count for something as they frantically search for a replacement for Popovic.

"I've had better Sunday mornings," he said, before suggesting that the recruitment process could be a lengthy one. "We'll take our time to make the right appointment."

However for Popovic, it was an opportunity that proved too good to refuse. A chance to coach in one of Europe's stronger leagues, at a club where he has been assured of having full control and the freedom to sign his own support staff, was one he couldn't refuse - even if it came at the cost of derailing the Wanderers' plans for the season.

"There's no great timing. It isn't great timing, we've spent 14-15 weeks of pre-season preparing a team that can challenge for the title - which I'm sure they will," he said. "But this has just come up last night and this morning, this is not something you can plan for. There's been a change of management overseas and I've been given the opportunity to take on that role. It's certainly not planned and I certainly understand the timing."

Karabukspor finished 12th in the Super Lig last season in their first year back at the top after promotion from the First League, but they are currently battling against relegation.

Located near the Black Sea, the team have won just once in seven games this season and sit third-last, a beginning to the season that cost coach Erkan Sozeri his job.

"This one was in a league which I think is in a very strong level - it's in Europe - and I want an opportunity to coach in Europe. It's an opening for me to do that and to have success in Turkey," Popovic said.

The Western Sydney Wanderers players are in disbelief with the abrupt departure of the Wanderers inaugural head coach.

The squad had not been told of the news from coaching staff, and had to learn of Popovic quitting on Sunday via social media. They are set to meet with Popovic and the coaching staff on Tuesday morning.

???The Wanderers players were on a day off after their season's launch on Saturday at Spotless Stadium, where Popovic ran an open training session in front of fans.