Referees and football commentators (not to mention the vast majority of fans) should do a spot of revision on the rules, especially with regards to handball and yellow card offences.
Yellow card offences:
A player is cautioned and shown the yellow card if he commits any of the following seven offences:
- unsporting behaviour
- dissent by word or action
- persistent infringement of the Laws of the Game
- delaying the restart of play
- failure to respect the required distance when play is restarted with a corner kick, free kick or throw-in
- entering or re-entering the field of play without the referee's permission
- deliberately leaving the field of play without the referee's permission
I guess when a player is booked for a "dirty" foul it is officially for unsporting behaviour or persistent infringement. If Byrne's "foul" was considered serious foul play or violent conduct then it should have been a straight red...which it wasn't. So, considering it was only his second foul of the night (I might be bullshitting here...he could have fouled more but I don't recall him persistently fouling) his second yellow (as well as the first) must have been for unsporting behaviour. Unsporting, presumably, in that he won the ball fair and square....