Sydney FC coach Graham Arnold is expecting an A-League quality showdown when his side play Sydney United in the FFA Cup.

Sydney FC coach Graham Arnold has told his players to prepare for Tuesday’s FFA Cup clash with former National Soccer League powerhouse Sydney United in the same way they would for an A-League derby.

The round of 16 tie is the most eagerly-anticipated match-up in the cup’s short history and offers a rare opportunity for a former giant of the national competition to bring down one of the A-League glamour clubs.

While Sydney United now play in state-based competition, Arnold has warned his players to be fully switched on when they visit Edensor Park in Sydney’s south-west, or risk embarrassment.

“I told the boys they need to prepare like it is a game against Western Sydney Wanderers, (if not) then we can get a kick up the backside,” Arnold said.

“It will be a tough game, a hostile crowd. It is not an easy place to play. I have played there in front of 10,000 people and it is quite daunting.

“We have to go out there with a tough mental attitude and character. We have to turn up with a perfect attitude.”

An unfamiliar synthetic pitch at the Sydney United Sports Centre offers an added challenge for Arnold’s team.

Arnold made his name at the Croatian community-backed club during the 1980s, spending nine productive seasons at the club which has produced dozens of Socceroos over the decades.

“I’m very grateful for the time I had at Sydney Croatia and the wonderful people I met there, but football is football, and the most important thing on my mind is Sydney FC,” Arnold said.

Current Sydney United coach Mark Rudan is a former Sydney FC captain.

The quarter-final line-up will be completed on Tuesday evening with three other fixtures being played across the country.

A-League title aspirants Adelaide United host champions Brisbane Roar in an early chance to claim bragging rights ahead of the season opener next month.

Brisbane have enjoyed a solid pre-season thus far but they will be without long-serving goalkeeper Michael Theo who was ruled out after suffering a wrist injury at training on Monday just prior to the team’s departure for Adelaide.

Gold Coast-based Palm Beach Sharks will be looking to avoid a banana skin when amateur third-tier Melbourne side South Springvale visit.

The challenge facing the visitors is heightened by the absence of Darragh Ryan and former Melbourne Victory midfielder Billy Damianos who were unable to get time off work.

In Melbourne St Alban Saints face a tough task when they host A-League side Perth Glory at Knights Stadium, home of former NSL champions Melbourne Knights.