Orange card

[xsnaggle]

Why not have penalty goals? similar thing works well in rugby, goal awarded and yellow card for perpetrator.

I can't see any downsides and would stop a game being ruined after X minutes by a side losing a player.

But penalty tries in Rugby are only awarded for a repeated offence to stop the opposition scoring a particular try, or for a blatant foul to prevent a try and this last one football already has with the last man ruling.
Sin binning can be applied across the field of play, and as Rjk says, a 10 minute binning for a yellow would certainly concentrate minds.