The Sky Blues bounced back from a midweek cup final defeat in Adelaide to down City 3-0 away on Friday night with 'Alfie' netting a brace to make it seven goals in all competitions.

The harbour-siders have been the powerhouse of Australian football for the past three years and are off to a flying start in season 2018/19 under new coach Steve Corica.

But after losing two key attacking imports in the off-season there were serious concerns that the goals could dry up. 

“I said before the season, it will be hard to replace Bobo and Adrian Mierzejewski, but Bobo especially, he scored 27 goals last season,” Ninkovic said.

“But maybe Adam will score more goals this year. The first year is always tough. I remember when I came, it wasn’t easy.

"I was surprised how Adam has adapted and he’s scored four goals in the last three games. He’s unbelievable.

“He is a different type of player than Bobo. Adam makes more forward runs. It was easy to play with Bobo, of course.

“I think the coaching staff did a very good job signing him and unfortunately Siem (de Jong) is injured, but he is also a very good player and I hope he is not going to be out for too long.”

Ninkovic is entering his fourth season with Sydney and enjoyed A-League championship and FFA Cup triumphs both in 2017.

The Serbian gelled well with reigning golden boot winner Bobo, who scored 42 goals in his time at Sydney and now plays his football in Turkey.

In the face of a massive roster upheaval, Ninkovic feels the team has exceeded expectations at the start of the new campaign.

Sydney topped the table last season, but were knocked out in the semi-final by arch-rivals Melbourne Victory in extra-time.

Ninkovic added: “If you remember our championship winning season, we lost only one game.

“We changed only one or two players. It was very easy to adapt because we kept most of the players, but this year we changed four or five new players and our coaching staff.

“I thought before the season, we would be great but we would need time to adapt. But I was surprised because we played the FFA Cup final and we are still at the top of the table, so I am proud of the team.”