Last week's MLS matches had several interesting offside decision that need analysis. As a group, PRO assistant referees need to make sure that on close offside decisions they are giving the benefit of doubt to the attack, that they are completely clear on the intricacies of Law 11 and that they are aware of certain free kick situations where offside can come into play.
The Flash Lag Effect on Offside Decisions
One of the reasons that PRO assistant referees are instructed to give the benefit of the doubt to the attack is because of the visual effect called flash-lag wherein a flash and a moving object that appear in the same location are perceived to be displaced from one another. This illustration demonstrates this effect. For assistant referees this is a real illusion that happens on the field almost every game. The "flash" being the pass and the circle being the location of the team mate.
Watch this offside decision in the DC United v Vancouver where the assistant referee, in excellent position, does not account for this effect and takes away an opportunity from Vancouver.
In Real Salt Lake v Colorado there was a similar situation, however not as extreme. Did the flash lag effect contribute to this decision?
An experienced AR will be ready for the quick movement of a defender to put an attacker in an offside position, and have adjusted for the flash lag effect as was done in this situation in Houston v Seattle.
The best way to combat this effect is awareness and regular visual training and practice. If you want to see how well you do will this visual effect, you can test yourself here.
Offside on Corner Kick Situations
Although everyone knows that there is no offside on a corner kick, assistants need to be ready for the second phase of play. In Houston v Seattle, Seattle believe that Houston is offside on this short corner. Closer analysis shows that the assistant was correct not to flag for offside. At the moment the Houston attacker steps on the ball (second phase of play) Houston's #10 Maidana has already moved far enough to have the goalkeeper and two defenders between him and the goal line.
ARs should mentally prepare themselves before corner kicks by checking if defenders are covering the post and be aware of the goalkeeper's movement and position.
Offside on Free Kick
The situation with a second wall of attackers was used by Philadelphia last weekend. Although I have included the play below, Paul Rejer, PRO Training and Development Manager, has provided his analysis in the PRO Play of the Week and can be reviewed here. To be clear, this is offside.
Offside? Difficult Decision in NYFC
A very difficult decision in NYFC v Chicago. The AR and referee confer because the assistant referee is not sure who has headed the ball after the free kick is taken. The referee confirms that is was played by an attacker and the assistant referee flags the far attacker for offside. An onside attacker does head the ball into goal, but has the offside player interfered with an opponent? Has he interfered with play? You decide.
An interesting situation went pretty much unnoticed in last week's Sporting Kansas City v NY Red Bull. Unfortunately there is no replay of this deliberate v. deflection offside decision. For sake of argument let's agree that SKC's Dwyer was in an offside position when the ball was last played by a team mate. He then comes from behind the NYRB defender, steals the ball and heads towards goal. Should he have been flagged for offside? From what can be seen in the video the NYRB defender has time and space to control the ball to his right, but misplays it where Dwyer is able to steal it. In my opinion, this is a deliberate play and Dwyer should not have been flagged. Do you agree? Vote below.
Assistant referees should not feel the need to quickly raise the flag in situations like this. Taking a moment to analyze the play before raising the flag is an important characteristic of the PRO assistant referee.