Complex sentence: At the East London club Etherington showed his true form and became a vital player for the "Hammers" however he also became addicted to gambling which led to Gianfranco Zola selling him to fellow Premier League side Stoke City in 2009.
Split into simpler sentences: At the East London club Etherington showed his true form and became a vital player for the "Hammers". However, his addiction to gambling led to Gianfranco Zola selling him to fellow Premier League side Stoke City in 2009.