#1 Lionel Messi
To be fair to Messi, he wasn't totally useless in Argentina's first game against Iceland. Rather, most of the criticism he has faced since has stemmed from the fact that his career rival Cristiano Ronaldo scored a hattrick 24 hours earlier.
Even so, it wasn't a vintage performance from the Barcelona number 10. As well as missing a penalty, he was generally unable to wriggle free from his Icelandic markers, constantly getting crowded off the ball as he attempted to play the decisive ball in the final third.
We should, however, see some significant improvement in his second and third matches in the competition. Having lost their first game to Croatia, Nigeria may need to attack Argentina when they meet on June 26, and this will leave space at the other end for Messi to exploit.