RateTheRef

4 of the VAR team are in the dedicated VAR centre. The VAR, AVAR, OVAR and SVAR. The SVAR takes over monitoring play developing if any of the other 3 are reviewing an incident. The SAVAR is at the ground where there is a back up VAR room in case the link/comms go down between the VAR centre and the ground.

If that were to happen the 4O moves into the VAR room in the ground and takes over as VAR with the SAVAR taking over as AVAR and the VAR team would operate as a team of 2 instead of 4. As well as being the reserve AR to replace an injured AR, the 5th official would also take over the role of 4O if the named 4O has to move into the ground based VAR room.

It therefore makes sense that they are actively involved with any substitutions etc and are maintaining a record of them, along with any cards issued etc. incase they have to step in as 4O.