A-League chief Damien de Bohun has defended the timing of the competition's transfer window which has left Sydney FC waiting on a gun striker they signed almost a month ago.The cellar-dwelling Sky Blues had former Newcastle Jets marquee Joel Griffiths signed, sealed and delivered on December 14.In seasons past, Griffiths would have joined Sydney FC when his contract with Shanghai Shenhua finished at the end of last year.However, under the current rules he's not allowed to start until Australia's transfer window opens on January 14.It's a situation Sydney FC coach Frank Farina, whose side are at the foot of the table and have been decimated by injury over the past month, labelled "crazy" and "strange" on Tuesday.De Bohun says changes to the transfer window dates made before last season were intended to help protect sides that had their brightest young stars poached by European clubs in the first two weeks of the year."The main rationale for this change was to allow clubs to sign new players during the relevant European registration windows," de Bohun said."While also allowing clubs to sign new players after the European registration periods close, enabling clubs to replace players that move late in the relevant transfer windows."Farina said the rule should be tweaked in cases like Griffiths', and Sydney FC chief executive Tony Pignata has already declared he will bring the issue up with Football Federation Australia."FFA has an ongoing dialogue with all clubs however a formal review process for league matters doesn't occur until the conclusion of the season," de Bohun said.Most Asian leagues' transfer periods have already started and Farina felt it was wrong for the FFA to force Griffiths to spend two weeks on the sidelines."I don't agree with the window here at the moment," Farina said after the Sky Blues' trained in sweltering heat on Tuesday."It's not as if he (Griffiths) is still contracted to a club - but he can't start playing until the 14th which, for me, is crazy."It's strange that he can't play for those two weeks."In good faith they put the dates down thinking it was going to be the best thing for the league but for us, in our situation, it's not."Farina, who promised to attack the competition's transfer window "rock hard", is still in the hunt for a central defender but admitted "it's a bit of a tall ask at this stage"."We can look hard but we've got to find one - one that's ready to play right now, and is available."