Coach Ian Crook warned Sydney FC will take time to develop his playing style after a bumbling display marred Alessandro Del Piero's much-hyped A-League debut.

An out-of-sorts Sydney looked static in defence and disjointed on attack, turning over the ball repeatedly when attempting a short passing game as they went down 2-0 to a far more convincing Wellington Phoenix in Wellington on Saturday.

They provided little in the way of service for Italy great Del Piero, who still managed to impress with his quality with his limited touches as he played the full match.

Sydney will want to improve markedly before turning out in front of home fans in Saturday's game against Newcastle at what's likely to be a packed Allianz Stadium.

The Phoenix were more fluent going forward, creating a raft of opportunities and converting two through former Belgium international Stein Huysegems and 19-year-old striker Louis Fenton.

Both Crook and captain Terry McFlynn admit Sydney failed to deliver, but said there was plenty of time - and room - for improvement.

"Football's all about results, about winning games," Crook said.

"But we believe we're making some substantial changes and we've got to keep looking at the positives and drive on from there."

In a patchy performance, Sydney battled to retain possession and were kept under pressure by a swarming Phoenix defensive effort.

"We turned the ball over a little bit too much... we did keep it, but probably not with the purpose we'd like which is to create a two-on-one somewhere on the pitch where we can use it," Crook said.

"It's a work in progress, you don't win or lose the league in one game. It's up to us to now go on and improve each week."

McFlynn says although Sydney performed in patches, they needed to develop more consistency and accuracy in maintaining possession and building pressure.

"We know tonight that it wasn't good enough to get a result, but we know what we have to do to be better," he said on Saturday.

"That starts on Monday - keeping the ball, getting forward with a purpose, supporting the front man from behind and putting the ball in the net."