Why not any other striker if it is much better?

FT: http://www.rubysoccer.com/game/match_report/519516

The defender was the best player available to take the penalty kick. The one who was better than him had received a red card.

But a defender shooting receive -3 in habilities at zone A, is not right?

i guess that is not applicable for penalties or freekicks..

The -3 penalty is applied if you put the defender on zone A in your formation, or use individual tactics to make him move forward to midfield…if you put him on defense in your formation and he ends up shooting during the match (including penalty kicks or free kicks) he will not receive any penalty.

Thank you!