Complex sentence: Club decided to change the head coach once again in the middle of 2012 season-due to the underperforming team and lack of enthusiasm on field, club's chair decided to offer head coach position to iconic star-striker Mikk Valtna.
Split into simpler sentences: Club decided to change the head coach once again in the middle of 2012 season-due to the underperforming team and lack of enthusiasm on field. Club's chair decided to offer the vacant head coach position to iconic star-striker Mikk Valtna.