Central Coast Mariners have announced they will appeal the lengthy suspension handed to goalkeeper Danny Vukovic for striking referee Mark Shield in the A-League grand final.Football Federation Australia Monday night slapped Vukovic with a 15-month ban for the incident, with six months of it suspended and only activated if he re-offends within a year of returning.Vukovic was shown a red card in Sunday night's 1-0 loss to Newcastle after hitting Shield on the arm when a late penalty appeal was turned down for what television replays showed was a hand ball by Jets midfielder James Holland.The Mariners said on Tuesday Vukovic was full of remorse but confirmed they would appeal the severity of the penalty."We can say that Danny deeply regrets his actions and he apologised to the referee immediately after the game verbally and today he has sent a formal written apology to the referee as well as to the referee's manager of the FFA and to the FFA," Mariners executive chairman Lyall Gorman said."I can say it's sincere. I think you all know Danny's record on and off the field and there's tremendous remorse in his action on the weekend."The club is of the view that the severity of the sanction for such a player of his record is excessive, despite the serious nature of the charge."Gorman said he had written to the FFA asking the appeal be heard as quickly as possible: "to put Danny's mind at ease and let both the club and Danny plan for the future."The Olyroos regular's ban threatens his chance to represent Australia at the Beijing Olympics in August with FFA still deciding whether the ban will extend beyond the A-League into national team duty.The Mariners also issued a formal apology after the FFA launched an investigation into an incident involving Andre Gumprecht and Tony Vidmar at the Mariners' end-of-year celebrations on Monday.Gumprecht appeared in a photograph dressed as Adolf Hitler while departing veteran Vidmar was dressed as 'God' with his face blackened.FFA CEO Ben Buckley described the players' actions as "stupid" while Jewish groups have labelled the stunt as being in poor taste.Gorman defended the character of both players, saying they did not mean to cause offence."The club has determined following speaking with both players that neither meant any offence or insensitivity with their costumes in any way," Gorman said."We've reinforced vigorously with the players today they need to be particularly careful in relation to sensitive issues which may cause offence to the public or particular sectors of it."To that extent, on behalf of the players if any groups were offended by their dress yesterday the club and the players apologise and reiterate that no such offence was intended."