The Russia national coach has arrived at Stamford Bridge until the end of the season following the sacking of Luiz Felipe Scolari, and will attempt to revitalise the Blues's title chances on Saturday when fourth-placed Chelsea face third-placed Aston Villa in the Midlands.
And opposing boss O'Neill is on the same page as Arsenal boss Arsene Wenger in believing Hiddink can be a success in west London in the short term, but will struggle to combine both jobs effectively beyond the end of the current campaign.
"It is incredibly hard," he told his club's official website. "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. 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."
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