The Dutchman has recently been appointed as Chelsea's new manager on a short-term deal which is set to run until the end of the season.
He will be combining his duties at Stamford Bridge with those he must undertake in his role as coach of the Russian national side.
With Chelsea still gunning for the Premier League title and UEFA Champions League crown, and Russia looking to book a safe passage through 2010 World Cup qualifying, Hiddink looks set to be a busy man over the course of the next few months.
O'Neill believes the dual role could prove to be successful if taken on for a short period of time, but believes any long-term plans to juggle two high-profile jobs could prove problematic.
Splitting time"It is incredibly hard," the Villa chief told his club's official website ahead of Saturday's showdown with the Blues.
"I think there might be a reason for doing it on a short-term basis.
"But overall, I think it would be very hard to combine an international management role with one in the Premier League over the fullness of time.
"I'm not sure that's what they are looking at (at Chelsea). Eventually, when you lose a game or two, someone will accuse you of not spending enough time in one particular camp.
"I think it is exceptionally difficult. Nothing is impossible. Over a short period of time, I'm sure it could work but over a three or four-year period, I think that would be particularly difficult."