Gerardo Martino admitted Copa America Group B winners Argentina were "boring" in the second half of their narrow 1-0 victory over Jamaica.
Argentina advanced to the quarter-finals as group winners after Gonzalo Higuain's 11th-minute strike inspired the pre-tournament favourites in Lionel Messi's 100th international appearance in Vina del Mar on Saturday.
Martino and Co. had countless opportunities to put the result beyond doubt but they were wasteful up front, while the crossbar denied both Higuain and Angel di Maria.
Speaking to reporters post-match, Martino - who watched from the stands after receiving a one-match ban for stepping onto the pitch against Uruguay - conceded his team have been far from their best in the competition so far.
"We are lacking effectiveness," Martino said. "It is something we took out of the result against Paraguay, but you cannot legislate for players of the ability of ours missing so many chances.
"The fact we didn't put the game to bed, coupled with the physical issues we are having towards the end of games, generated uneasiness.
"I thought we did alright in the first half, getting the early goal and then creating four or five chances to score. We also did well to control Jamaica’s chances to break. But the second half was boring, our ball control was tedious, the movement of the ball was too slow and we generally lacked speed in processing our play."
Argentina will play either Ecuador or the third-placed team from Group C on June 26.
