Complex sentence: Domestic Cup competitions show further unpredictable form: they were defeated in the Carling Cup Second round to Brighton & Hove Albion of League One on penalties, while in the FA Cup City faced Nottingham Forest at home in the Third round proper and lost 3--0.
Split into simpler sentences: Domestic Cup competitions show inconsistencies: they were defeated in the Carling Cup second round to Brighton & Hove Albion of League One on penalties. In the FA Cup, City faced Nottingham Forest at home in the third round proper and lost 3--0.