Two free kicks effectively secured the Japanese their second round place on Thursday but they could have scored more after dominating much of the match.
Olsen, however, was in no mood to pay tribute to the Asians afterwards at the Royal Bafokeng Stadium.
"It was not a matter of a good Japan or a poor Denmark, it was just unnecessary what happened," he told a news conference.
"Beforehand I underlined the importance of the first goal and when (Keisuke) Honda struck it became an uphill struggle for us.
"We knew that they had two players who could execute and we couldn't prevent it," he added.
Denmark finished top of a tough qualifying group containing Portugal and Sweden but a long list of injuries including one which hampered their main strike threat Niklas Bendtner seemed to take the wind out of their sails in South Africa.
The 1992 European champions never remotely approached the early dynamism of their campaigns in the 1986, 1998 and 2002 finals.
"We started well tonight, created the first chance and that gave us a good feeling but after the opening goal we were just chasing the game," skipper Jon Dahl Tomasson told Reuters.
"After the second goal it was all over."
Denmark finished third following an opening defeat by Group E winners Netherlands and a 2-1 win over Cameroon in a game which could have gone either way.
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