Sydney FC were notified by the FFA that Del Piero breached A-League regulations by using the armband for possible promotional purposes, as it displays his company's image and replicas are sold through his online store for $23.

Del Piero appeared to be wearing one of the two armband designs approved and provided by the FFA but upon closer inspection, a watermark "ADP" logo can be seen. The subtly printed logo is not clear in daylight but becomes visible in images and in certain light as it contrasts with the background colour.

As with the English Premier League, the A-League has strict rules that standardise captains' armbands and prevent players from wearing custom designs that may display advertisements, messages or images.

By contrast, the Italian Serie A, where Del Piero played more than 19 seasons, is more relaxed, as clubs often provide their own armbands and players have been known to wear personalised items. While at Juventus, Del Piero often wore a band that displayed his jersey number while some players have even been known to wear designs with religious messages. Former Brescia captain Roberto Baggio wore an armband with a buddhist flag.

The A-League's regulations state: "Captains' armbands shall remain free of a sponsor, and decorative element or further elements, except for the word 'captain’ or an abbreviation or translation thereof."

An FFA spokesman confirmed Sydney FC had been notified about the breach of the regulations . Neither the club or the player will be punished or sanctioned but the 39-year-old will be forced to wear the A-League standard armbands for the remainder of the season.

“FFA has been made aware that the Sydney FC Captain’s Armband carried unauthorised wording and has written to Sydney FC advising the club the armband contravenes the Competition Regulations and should not be used,” an FFA spokesman said.

Sydney FC chief executive Tony Pignata said the club was unaware its star player was wearing a custom armband and would not contest the FFA's order.

"We received a letter from the FFA regarding Alessandro, the club wasn't aware of it but we will comply with it," Pignata said.

It is not the first time the FFA has prevented Sydney's marquee player from promoting his personal logo during games by wearing equipment displaying his image.

It's understood that Del Piero was advised last season to turn two sweatbands inside out as they both displayed his brand. The former Juventus star regularly wears two coloured sweatbands also sold on his website, one orange and the other blue, and was told early in his A-League career to hide the logo or take the bands off during games.

In November 2012, former Sydney FC forward Yairo Yau said he was instructed to stop wearing sweat bands displaying the Panamanian flag.