Complex sentence: Guardiola played as a defensive midfielder and spent the majority of his playing career with FC Barcelona, whom he managed for four years and breaking numerous records before announcing his intention to quit at the end of the 2011-12 season on 27 April 2012.
Split into simpler sentences: Guardiola played as a defensive midfielder and spent the majority of his playing career with FC Barcelona. Guariola has managed Barcelona for four years and has broken numerous records; he announcing his resignation at the end of the 2011-12 season on 27 April 2012.