Maybe a yellow to Manny while on the park, but not now - not after O'Donovan also got a yellow for his indiscretion.
An elbowing can be seen as something done in a heat of the close tackle and a benefit of the doubt can be applied regarding "deliberate elbow". While it was not pretty or desirable, we've also been dealt that and more with fouls in every game against Roly, Roy, Siggy being smashed. Would you blame Fenton if he is feeling tentative about tackles now that he has two dodgy shoulders?
The clip from the New Year's Eve showing O'Donovan's headbutt can be gleefully replayed forever for all to see what thuggery goes unpunished in A-League, whether "provoked" or not. And this is a reason - apart from the issue of justice to Manny - that this needs to be dealt with in an exemplary way. Otherwise FFA can kiss its "family entertainment" promotion goodbye, together with any attempt to lure skilful guest / marquee players.
A very public if largely harmless headbutt ended Zidane's playing days, even if it was "provoked" or "deserved".
And O'Donovan is not Zidane - he is a minor league thug that needs to learn some respect.