Adelaide FC coach Gertjan Verbeek criticised his team's lack of focus for their 2-1 loss to Central Coast on Sunday night.

The fifth-placed Reds were stunned by two goals in the first half against the then-bottom-placed Mariners - and it's not the first time it's happened in this A-League season.

It's a concern for Verbeek, who said his team don't have the class not to perform at their best each week and still come away with a win.

The Reds were also beaten 2-1 by Wellington Phoenix in round 8 when the trans-Tasman side were last on the ladder, and Verbeek puts it down to an inability to match their opponent's mentality.

"I think it's the same with Central Coast. If you don't have the attitude and the mentality the same as the opponents, you can lose every game," he said.

"It's the same for us. We don't have the extra quality that we say we can have an off day and we can still win it.

"I think Sydney have that, Perth have that and maybe City, but we don't. We have to be top every game, if not, we can lose."

It's the second loss in three weeks for the Reds who will now host Markus Babbel's Western Sydney Wanderers in Perth next week.

Verbeek's biggest task will be mentally preparing his side to rise to the challenge against a team under pressure.

"(I hope) that they learn from this game and they understand that if they're not ready for the game or 1000 per cent focused on what to do, then we have a real chance to lose it," he said.

"We can do it, the focus has to be OK, but we have to know that we have to do it together as a team and everybody has to give 100 per cent.

"And if not, we are vulnerable."