Despite creating chances in Canberra the Frenchman's charges were beaten by a Cho Young-cheol strike in first-half stoppage time.
However, Le Guen felt his side's efforts to get back into the game against one of the stronger teams in the competition shows there is plenty to work in the coming fixtures.
"I am never totally satisfied when we lose but I know that they gave their best and they fought on the pitch," he said. "It's hard luck, congrats to South Korea they deserved to win.
"I am disappointed because we were so close we had chances, clear chances and against such a team it's not nothing. It proves we are on the right way we are improving but it is not enough.
"We have tried until the end until the last minute we wanted to come back and realty I liked the fighting spirit we had on the pitch and I know that was not enough."
Oman face hosts Australia in their next fixture, needing something to give them a fighting chance of making it out of the group.
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