Rio Ferdinand has told BT Sport that Per Mertesacker should shoulder most of the blame for Barcelona's second - and potentially decisive - goal against Arsenal at the Emirates Stadium on Tuesday night.
The midfielder's tackle on the Argentine came less than a minute after being introduced as a substitute and there was little doubt that the referee made the correct decision in pointing to the spot.
However, former Manchester United defender Ferdinand feels that the situation could have been averted had Mertesacker opted to clear the ball, rather than attempt to cushion it to his teammate inside his own 18-yard area.
Ferdinand said: "It was crazy. Per Mertesacker will probably take most of the blame for his touch and for bringing the ball down in his box. You are told as a kid to get rid and see what is around.
"Obviously Flamini has come on and he is not up to the speed of the game, but when Messi is around, he is so quick to smell an opportunity and draws the foul."
The penalty was calmly slotted into the corner by Messi to hand Barcelona a commanding advantage ahead of the second leg, which takes place in Spain on March 16.
If Arsenal are unable to overturn the two-goal deficit, they will bow out of the competition at the last-16 stage for the sixth year in succession.