When Police arrive on scene to a DV, they separate the parties involved. They are supposed to weigh both stories, look at any physical evidence, bruises blood etc, witness accounts etc, then they decide if they have PC (Probable cause to make an arrest).
If you have someone who does not speak the local language correctly and there is not a Officer on scene who in in this case (if he did not speak fluent) it could be argued that Roberto made spontaneous statements without understanding his rights, the question, the instructions of the Officer.. He was not able to articulate that the bruises etc are due to self defense and the crazy chica attack him etc.. In the US you have Miranda Rights etc.
What I was saying, is that when there is a language barrier, your attorney might have more wiggle room to do some attorney s***. If he can get the arrest PC actions invalidated, he could get the charges thrown out. No charges would obviously make a difference in the team's and MLBs actions towards Osuna.