this, a few people seem to challenge their next opponent in cup/cleague to a friendly sometimes a day or two before it to see whethor they need to strengthen their squad so a lot of people will put all their players on with hard tackling and put all their players in a position near your top players to try and injure them before the proper game since nothing happens to them if they are playing an away friendly. I had a friendly against some guy in my league last season and 3 of my top 5 players got injured after he finished with 9 men