The Argentine-born coach was not pleased with Paraguay's performance in a disappointing 0-0 draw against New Zealand that was enough to take them into the last 16.
They now face Japan in the second round on Tuesday.
"We were not very mobile and we were quite inaccurate," he told reporters after the match. "We had a lot of problems in an area where we didn't expect, and that was in attack."
They were solid in defence though, conceding only one goal in three matches against Italy in the first game.
"I think Paraguay had an excellent aspect to the defensive part in the three matches, we were very good defensively," Martino said.
Paraguay, ranked 31st in the world by FIFA, topped Group F but managed just one win against Slovakia and scored only three goals despite a trio of top-class strikers in Roque Santa Cruz, Lucas Barrios and Nelson Valdez.
All three were on the field at the end of the New Zealand game and yet they failed to convert a number of opportunities.
Martino said the side would have to raise their game to get through to the quarter-finals.
Last 16 opponents Japan overpowered Denmark on Thursday, scoring three goals and have been transformed from the side that lost a series of friendlies leading into the tournament.
Santa Cruz said the players were not happy with their showing against New Zealand but the important thing was that they had made it through the group.
"Maybe today we had the feeling that we weren't altogether happy with ourselves .. we had opportunities and we should have put them away," he said.
"I think we were not as patient as we should have been."
Santa Cruz said a quarter-final berth would be a job well done for Paraguay but added that once they were there, anything was possible.
"We would have considered it a very good World Cup if we were to get to the quarter-finals, that for us is good enough and after that it is a dream," he said.
"But we have the wherewithal to make it further." (Editing by Michael Holden)
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