With Messi as coach Argentina were definitely noticeably better against Nigeria. They actually created scoring chances and had some instances of good interplay but it was still a lucky win as their defense was lolsworthy. Had a number of anxious moments were a mistake almost let Nigeria score. Game very easily could have been a loss for them and that kind of play will be punished by someone better than Nigeria.
Usually to win a tournament like this you've got to have a much more functional defense than Argentina do.